LaravelConf Taiwan 2019 announcement

# Math Functions

• abs — Absolute value
• acos — Arc cosine
• acosh — Inverse hyperbolic cosine
• asin — Arc sine
• asinh — Inverse hyperbolic sine
• atan2 — Arc tangent of two variables
• atan — Arc tangent
• atanh — Inverse hyperbolic tangent
• base_convert — Convert a number between arbitrary bases
• bindec — Binary to decimal
• ceil — Round fractions up
• cos — Cosine
• cosh — Hyperbolic cosine
• decbin — Decimal to binary
• dechex — Decimal to hexadecimal
• decoct — Decimal to octal
• deg2rad — Converts the number in degrees to the radian equivalent
• exp — Calculates the exponent of e
• expm1 — Returns exp(number) - 1, computed in a way that is accurate even when the value of number is close to zero
• floor — Round fractions down
• fmod — Returns the floating point remainder (modulo) of the division of the arguments
• getrandmax — Show largest possible random value
• hexdec — Hexadecimal to decimal
• hypot — Calculate the length of the hypotenuse of a right-angle triangle
• intdiv — Integer division
• is_finite — Finds whether a value is a legal finite number
• is_infinite — Finds whether a value is infinite
• is_nan — Finds whether a value is not a number
• lcg_value — Combined linear congruential generator
• log10 — Base-10 logarithm
• log1p — Returns log(1 + number), computed in a way that is accurate even when the value of number is close to zero
• log — Natural logarithm
• max — Find highest value
• min — Find lowest value
• mt_getrandmax — Show largest possible random value
• mt_rand — Generate a random value via the Mersenne Twister Random Number Generator
• mt_srand — Seeds the Mersenne Twister Random Number Generator
• octdec — Octal to decimal
• pi — Get value of pi
• pow — Exponential expression
• rad2deg — Converts the radian number to the equivalent number in degrees
• rand — Generate a random integer
• round — Rounds a float
• sin — Sine
• sinh — Hyperbolic sine
• sqrt — Square root
• srand — Seed the random number generator
• tan — Tangent
• tanh — Hyperbolic tangent

### User Contributed Notes 52 notes

nazgul26 (at_sign) windfox dot net
16 years ago
``` This code will convert a decimal to it's fraction equivalent. The precision can be set by changing PRECISION. <?php define(PRECISION, .01); \$count=0; \$result=array(); decimalToFraction(\$_REQUEST['dec'],\$count,&\$result); \$count = count(\$result); \$simp_fract = simplifyFraction(\$result,\$count,1,\$result[\$count]); echo \$simpl_fract; // Start of functions /*    Converts a decimal to unsimplified fraction represented in an array */ function decimalToFraction(\$decimal,\$count,\$result) {     \$a = (1/\$decimal);     \$b = ( \$a - floor(\$a)  );     \$count++;     if (\$b > .01 && \$count <= 5) decimalToFraction(\$b,\$count,&\$result);     \$result[\$count] = floor(\$a); } /*     Simplifies a fraction in an array form that is returned from      decimalToFraction */ function simplifyFraction(\$fraction,\$count,\$top,\$bottom) {     \$next = \$fraction[\$count-1];     \$a = (\$bottom * \$next) + \$top;     \$top = \$bottom;     \$bottom = \$a;     \$count--;     if (\$count > 0) simplifyFraction(\$fraction,\$count,\$top,\$bottom);     else {         return "<font size=1>\$bottom/\$top</font>";     } } ?> ```
Anonymous
1 year ago
``` And the reason I needed a Factorial function is because I there were no nPr or nCr functions native to PHP, either.function n_pick_r(\$n,\$r){\$n=(int)\$n; \$r=(int)\$r;return (fact(\$n)/fact(\$n-\$r));}function n_choose_r(\$n,\$r){\$n=(int)\$n; \$r=(int)\$r;return (n_pick_r(\$n,\$r)/fact(\$r));}Hope that helps someone!exmple:https://vb.3dlat.com/ ```
peter-stangl at t-online dot de
13 years ago
``` I needed to approximate an integral because i was not able to calculate it, so i wrote this function. It approximates an integral with the composite Simpson's rule.More information on Simpson's rule: http://en.wikipedia.org/wiki/Simpson%27s_rule<?phpfunction simpsonf(\$x){// returns f(x) for integral approximation with composite Simpson's rule   return(pow((1+pow(\$x, (-4))), 0.5));}function simpsonsrule(\$a, \$b, \$n){// approximates integral_a_b f(x) dx with composite Simpson's rule with \$n intervals// \$n has to be an even number// f(x) is defined in "function simpsonf(\$x)"   if(\$n%2==0){      \$h=(\$b-\$a)/\$n;      \$S=simpsonf(\$a)+simpsonf(\$b);      \$i=1;      while(\$i <= (\$n-1)){         \$xi=\$a+\$h*\$i;         if(\$i%2==0){            \$S=\$S+2*simpsonf(\$xi);         }         else{            \$S=\$S+4*simpsonf(\$xi);         }         \$i++;      }      return(\$h/3*\$S);      }   else{      return('\$n has to be an even number');   }}?> ```
-1
sabry97000 at gmail dot com
10 months ago
``` And the reason I needed a Factorial function is because I there were no nPr or nCr functions native to PHP, either.function n_pick_r(\$n,\$r){\$n=(int)\$n; \$r=(int)\$r;return (fact(\$n)/fact(\$n-\$r));}function n_choose_r(\$n,\$r){\$n=(int)\$n; \$r=(int)\$r;return (n_pick_r(\$n,\$r)/fact(\$r));}Hope that helps someone!exmple www.pqlme.com php ```
-1
jbeardsl [found_at] gte [d0t] net
16 years ago
``` I was looking for a truncate function. Not finding one, I wrote my own. Since it deals with everything as a number, I imagine it's faster than the alternative of using string functions. HTH... <?php function truncate (\$num, \$digits = 0) {     //provide the real number, and the number of     //digits right of the decimal you want to keep.     \$shift = pow(10, \$digits);     return ((floor(\$num * \$shift)) / \$shift); } ?> ```
-1
tmpa at yahoo dot com
14 years ago
``` while joogat's one line function is short, it is probably better to calculate factorial iteratively instead of recursively. keep in mind if you want large factorials, you'll need to use some sort of arbitrary precision integer or perhaps the BCMath functions. then again, unless you're trying to do large numbers (170! is the highest that you can do that does not return infinity) you probably won't notice any time difference.<?phpfunction factorial(\$in) {    // 0! = 1! = 1    \$out = 1;    // Only if \$in is >= 2    for (\$i = 2; \$i <= \$in; \$i++) {        \$out *= \$i;    }    return \$out;}?> ```
-1
webkid%webkid.com
17 years ago
``` And the reason I needed a Factorial function is because I there were no nPr or nCr functions native to PHP, either.function n_pick_r(\$n,\$r){\$n=(int)\$n; \$r=(int)\$r;return (fact(\$n)/fact(\$n-\$r));}function n_choose_r(\$n,\$r){\$n=(int)\$n; \$r=(int)\$r;return (n_pick_r(\$n,\$r)/fact(\$r));}Hope that helps someone! ```
-1
pat.mat AT sympatico DOT com
15 years ago
``` For people interest in Differential Equations, I've done a function that receive a string like: x^2+x^3 and put it in2x+3x^2 witch is the differantial of the previous equation.In the code there is one thing missing: the \$string{\$i} is often going outOfBound (Uninitialized string offset: 6 in...)if your error setting is set a little too high... I just dont know how to fix this.So there is the code for differential equation with (+ and -) only:<?function differentiel(\$equa){    \$equa = strtolower(\$equa);    echo "Equation de depart: ".\$equa."<br>";    \$final = "";         for(\$i = 0; \$i < strlen(\$equa); \$i++)    {        //Make a new string from the receive \$equa        if(\$equa{\$i} == "x" && \$equa{\$i+1} == "^")        {            \$final .= \$equa{\$i+2};            \$final .= "x^";            \$final .= \$equa{\$i+2}-1;        }        elseif(\$equa{\$i} == "+" || \$equa{\$i} == "-")        {            \$final .= \$equa{\$i};        }        elseif(is_numeric(\$equa{\$i}) && \$i == 0)        {            //gerer parenthese et autre terme generaux + gerer ^apres: 2^2            \$final .= \$equa{\$i}."*";        }        elseif(is_numeric(\$equa{\$i}) && \$i > 0 && \$equa{\$i-1} != "^")        {            //gerer ^apres: 2^2            \$final .= \$equa{\$i}."*";        }        elseif(\$equa{\$i} == "^")        {            continue;        }        elseif(is_numeric(\$equa{\$i}) && \$equa{\$i-1} == "^")        {            continue;        }        else        {            if(\$equa{\$i} == "x")            {                \$final .= 1;            }            else            {                \$final .= \$equa{\$i};             }        }    }    //    //Manage multiplication add in the previous string \$final    //    \$finalMul = "";    for(\$i = 0; \$i < strlen(\$final); \$i++)    {        if(is_numeric(\$final{\$i}) && \$final{\$i+1} == "*" && is_numeric(\$final{\$i+2}))        {            \$finalMul .= \$final{\$i}*\$final{\$i+2};        }        elseif(\$final{\$i} == "*")        {            continue;        }        elseif(is_numeric(\$final{\$i}) && \$final{\$i+1} != "*" && \$final{\$i-1} == "*")        {            continue;        }        else        {            \$finalMul .= \$final{\$i};            }    }    echo "equa final: ".\$finalMul;}?>I know this is not optimal but i've done this quick :)If you guys have any comment just email me.I also want to do this fonction In C to add to phpCore maybe soon...Patoff ```
-1
help at gjbdesign dot com
14 years ago
``` Occasionally a user must enter a number in a form. This function converts fractions to decimals and leaves decimals untouched. Of course, you may wish to round the final output, but that is not included here.<?php/*Some example values of \$q\$q = "2.5";\$q = "2 1/2";\$q = "5/2";*/function Deci_Con(\$q){//check for a space, signifying a whole number with a fraction    if(strstr(\$q, ' ')){        \$wa = strrev(\$q);        \$wb = strrev(strstr(\$wa, ' '));        \$whole = true;//this is a whole number    }//now check the fraction part    if(strstr(\$q, '/')){        if(\$whole==true){//if whole number, then remove the whole number and space from the calculations              \$q = strstr(\$q, ' ');        }\$b = str_replace("/","",strstr(\$q, '/'));//this is the divisor//isolate the numerator\$c = strrev(\$q);\$d = strstr(\$c, '/');\$e = strrev(\$d);\$a = str_replace("/","",\$e);//the pre-final numerator        if(\$whole==true){//add the whole number to the calculations            \$a = \$a+(\$wb*\$b);//new numerator is whole number multiplied by denominator plus original numerator            }\$q = \$a/\$b;//this is now your decimalreturn \$q;    }else{        return \$q;//not a fraction, just return the decimal    }}?> ```
-1
monte at ohrt dot com
13 years ago
``` This is an efficient method of calculating the binomial coefficient C(n,k). This code was derived from Owant: Mastering Algorithms with Perl.<?php   // calculate binomial coefficient   function binomial_coeff(\$n, \$k) {      \$j = \$res = 1;      if(\$k < 0 || \$k > \$n)         return 0;      if((\$n - \$k) < \$k)         \$k = \$n - \$k;      while(\$j <= \$k) {         \$res *= \$n--;         \$res /= \$j++;      }      return \$res;   }?>If you compiled php with --enable-bcmath, you can get full integer values of extremely large numbers by replacing:\$res *= \$n--;\$res /= \$j++;with:\$res = bcmul(\$res, \$n--);\$res = bcdiv(\$res, \$j++); ```
-2
bjcffnet at gmail dot com
13 years ago
``` thearbitcouncil at gmail dot com, you could just use array_sum():<?phpfunction average(\$arr){   if (!is_array(\$arr)) return false;   return array_sum(\$arr)/count(\$arr);}\$array = array(5, 10, 15);echo average(\$array); // 10?> ```
-2
edward at edwardsun dot com
12 years ago
``` well just a note.. maybe i'm a bit stupid.. but remember to use pow() rather than the "^" sign for exponents.. as it took me 5 minutes to figure out why it wasn't working. ```
-2
florian at shellfire dot de
15 years ago
``` Please note that shorter is not always better (meaning that really short faculty implementation above). In my opinion, a clearer way to code this is, including a check for negative or non-integer values. In order to calculate the faculty of a positive integer, an iterative way (which might be harder to understand) is usually a bit faster, but I am using it only for small values so it is not really important to me: <?php     // Calculate the Faculty of a positive int-value     function iFaculty(\$a_iFac)     {       if (\$a_iFac > 0)       {           return \$a_iFac * \$this->iFaculty(\$a_iFac - 1);       }       elseif (\$a_iFac == 0)       {           return 1;       }       else       {           return 0;  // Wrong argument!       }     } ?> I've also written another function to calculate the binomial coefficient of 2 values, I didn't find it anywhere yet so I hope it might help someone (works fine with the above stated faculty-function and ready to be used inside of your own classes!) <?php     // calculates the binomial coefficient "n over k" of 2 positive int values     // for n >= k     function iBinCoeff(\$a_iN, \$a_iK)     {         // the binomial coefficient is defined as n! / [ (n-k)! * k! ]         return \$this->iFaculty(\$a_iN) / (\$this->iFaculty(\$a_iN - \$a_iK) * \$this->iFaculty(\$a_iK));        } ?> ```
-2
jerry dot wilborn at fast dot net
16 years ago
``` Here is how to calculate standard deviation in PHP where \$samples is an array of incrementing numeric keys and the values are your samples:\$sample_count = count(\$samples);for (\$current_sample = 0; \$sample_count > \$current_sample; ++\$current_sample) \$sample_square[\$current_sample] = pow(\$samples[\$current_sample], 2);\$standard_deviation = sqrt(array_sum(\$sample_square) / \$sample_count - pow((array_sum(\$samples) / \$sample_count), 2)); ```
-1
jl85 at yahoo dot com
15 years ago
``` Here's yet another greatest common denominator (gcd) function, a reeeeally small one.function gcd(\$n,\$m){if(!\$m)return\$n;return gcd(\$m,\$n%\$m);}It works by recursion. Not really sure about it's speed, but it's really small! This won't work on floating point numbers accurately though. If you want a floating point one, you need to have at least PHP 4, and the code would befunction gcd(\$n,\$m){if(!\$m)return\$n;return gcd(\$m,fmod(\$n,\$m));} ```
-1
ian at mp3 dot com
18 years ago
``` for those looking for a credit card verification function i wrote a simple LUHN Formula algorithm: <?php \$valid = 1; \$numOfDigits = 0 - strlen(\$ccNumber); \$i = -1; while (\$i>=\$numOfDigits){   if ((\$i % 2) == 0){     \$double = 2*(substr(\$ccNumber, \$i, 1));     \$total += substr(\$double,0,1);     if (strlen(\$double > 1)){       \$total += substr(\$double,1,1);     }   } else {     \$total += substr(\$ccNumber, \$i, 1);   }   \$i--; } if ((\$total % 10) != 0){   \$valid = 0; } ?> ```
-2
Mike
11 years ago
``` //had a mistake in last post, heres the corrected version/*Just a simple function to trim digits from the left side of an integer. TRIM DOWN TO 4-> (ie. 987654 => 7654)*/function trimInteger(\$targetNumber,\$newLength) {    \$digits = pow(10,\$newLength);    \$s = (\$targetNumber/ \$digits); //make the last X digits the                  decimal part    \$t = floor(\$targetNumber / \$digits); //drop the last X digits (the decimal part)    \$h = \$s - \$t; //remove all  but the decimal part    \$newInteger = (\$h*\$digits); //make the everything after the decimal point the new number    return \$newInteger;} ```
-2
moikboy (nospam!) moikboy (nospam!) hu
13 years ago
``` I think, this is the optimal code for calculating factorials:<?phpfunction fact(\$int){    if(\$int<2)return 1;    for(\$f=2;\$int-1>1;\$f*=\$int--);    return \$f;};?>And another one for calculating the \$int-th Fibonacci-number:<?phpfunction fib(\$int){    static \$fibTable=array();    return empty(\$fibTable[\$int])?\$fibTable[\$int] = \$int>1?fib(\$int-2)+fib(\$int-1):1:\$fibTable[\$int];};?> ```
-2
info at gavinvincent dot co dot uk
14 years ago
``` If you need to deal with polar co-ordinates for somereason you will need to convert to and from x,y for input and output in most situations: here are some functions to convert cartesian to polar and polar to cartesian<?//returns array of r, theta in the range of 0-2*pi (in radians)function rect2polar(\$x,\$y){     if(is_numeric(\$x)&&is_numeric(\$y))    {        \$r=sqrt(pow(\$x,2)+pow(\$y,2));        if(\$x==0)        {             if(\$y>0) \$theta=pi()/2;            else \$theta=3*pi()/2;        }        else if(\$x<0) \$theta=atan(\$y/\$x)+pi();        else if(\$y<0) \$theta=atan(\$y/\$x)+2*pi();        else \$theta=atan(\$y/\$x);        \$polar=array("r"=>\$r,"theta"=>\$theta);        return \$polar;    }    else return false;}//r must be in radians, returns array of x,yfunction polar2rect(\$r,\$theta){ if(is_numeric(\$r)&&is_numeric(\$theta)) {        \$x=\$r*cos(\$theta);    \$y=\$r*sin(\$theta);    \$rect=array("x"=>\$x,"y"=>\$y); } else {   return false; }}?> ```
-2
fabien_mornand at yahoo dot fr
15 years ago
``` here is an algorithm to calculate gcd of a number. This is Euclid algorithm i was studying in Maths. I've converted it in php for the fun.<?php if(\$a && \$b)  { \$ax=\$a; \$bx=\$b;   \$r=fmod(\$a,\$b);  if(!\$r){\$rx=\$r;}   while(\$r){    \$rx=\$r;    \$a=\$b;    \$b=\$r;    \$r=fmod(\$a,\$b);    }   }echo 'PGCD ('.\$ax.' , '.\$bx.' ) = '.\$rx;?> ```
-3
php at keith tyler dot com
8 years ago
``` Another ordinal method, which does not involve utilizing date functions:<?phpsprintf( "%d%s", \$t, array_pop( array_slice( array_merge( array( "th","st","nd","rd"), array_fill( 4,6,"th")), \$t%10, 1)));'?> ```
-3
capripot at gmail dot com
6 years ago
``` Another simpler function to check a number with the luhn algorithm : <?php function luhn(\$num){     if(!\$num)         return false;     \$num = array_reverse(str_split(\$num));     \$add = 0;     foreach(\$num as \$k => \$v){         if(\$k%2)             \$v = \$v*2;         \$add += (\$v >= 10 ? \$v - 9 : \$v);     }     return (\$add%10 == 0); } ?> Don't know if foreach and arrays operations are faster than while and substr, but I feel it clearer. ```
-2
Aiden880
4 years ago
``` Lowest Common Denominator:function lcd(\$num, \$start) {    while(\$num % \$start != 0) {        \$start++;    }    return \$start;} ```
-2
Florian
13 years ago
``` A function that simulates the sum operator. (http://en.wikipedia.org/wiki/Sum). Be careful with the expression because it may cause a security hole; note the single quotes to don't parse the "\$".<?php# @param    string    \$expr    expression to evaluate (for example (2*\$x)^2+1)# @param    string    \$var      dummy variable (for example "x")# @param    integer    \$start# @param    integer    \$end# @param    integer    \$stepfunction sum(\$expr,\$var,\$start,\$end,\$step = 1) {    \$expr = str_replace(';','',\$expr);    \$var = str_replace('\$','',\$var);    \$start = (int)\$start;    \$end = (int)\$end;    \$step = (int)\$step;    \$sum = 0;        for (\$i = \$start; \$i <= \$end; \$i = \$i + \$step) {        \$_expr = str_replace('\$'.\$var,\$i,\$expr);            \$_eval = '\$_result = '.\$_expr.'; return \$_result;';        \$_result = eval(\$_eval);        if(\$result === FALSE) return "SYNTAX ERROR : \$expr";        \$sum += \$_result;    }    return (int)\$sum;}?> ```
-2
jl85 at yahoo dot com
16 years ago
``` Theres another faster way of doing even/odd number checking by using bitwise operators. Don't ask me how it works, I just found this out by experimenting with it (could the editor possibly explain?)if ((1&\$num)) { echo "\$num is odd";}if (!(1&\$num)) { echo "\$num is even";}How it works is (1&\$num) returns a 1 for odd numbers and returns 0 when it's an even number. ```
-2
patience at worldonline dot nl
16 years ago
``` The example for Factorials given above is wrong. Here a correct version, so that you do not have to reinvent the wheel again... <?php function mathFact( \$s ) {   \$r = (int) \$s;   if ( \$r < 2 )     \$r = 1;   else {     for ( \$i = \$r-1; \$i > 1; \$i-- )       \$r = \$r * \$i;   }   return( \$r ); } ?> ```
-2
AsherMaximum gmail
8 years ago
``` Here's a simple way way to convert a number to an ordinal number I created: \$i == the number to convert. Put this inside a for loop if you need to populate an array. <?php // change increment variable to ordinal number. \$n1 = \$i % 100; //first remove all but the last two digits \$n2 = (\$n1 < 20 ? \$1 : \$i % 10; //remove all but last digit unless the number is in the teens, which all should be 'th' //\$n is now used to determine the suffix. \$ord = (\$n2==1 ? \$i.'st' : ( (\$n2==2 ? \$i.'nd' : (\$n2==3 ? \$i.'rd' : \$i.'th') ) ) ) ?> ```
-2
barry at megaspace dot com
12 years ago
``` Here's a least common denominator (lcd) function:\$array = array(3,4,6,8,18,2);        function lcd(\$array,\$x) {                        \$mod_sum = 0;                for(\$int=1;\$int < count(\$array);\$int++) {                            \$modulus[\$int] = (\$array[0]*\$x) % (\$array[\$int]);            \$mod_sum = \$mod_sum + \$modulus[\$int];                    }                     if (!\$mod_sum) {            echo "LCD: ".(\$array[0]*\$x)."\n";        }                    else {            lcd(\$array,\$x+1);        }            }lcd(\$array,1); ```
-2
daniel at g-loc dot org
13 years ago
``` If you're an aviator and needs to calculate windcorrection angles and groundspeed (e.g. during flightplanning) this can be very useful. \$windcorrection = rad2deg(asin(((\$windspeed * (sin(deg2rad(\$tt - (\$winddirection-180))))/\$tas)))); \$groundspeed = \$tas*cos(deg2rad(\$windcorrection)) + \$windspeed*cos(deg2rad(\$tt-(\$winddirection-180))); You can probably write these lines more beautiful, but they work! ```
-4
thearbitcouncil at gmail dot com
14 years ago
``` Two functions I didn't find elsewhere... one to compute mean of an array of numbers, and another to computer variance of a sample of numbers. Both take an array of numbers as arguments. Not much error checking, or optimization...(note: variance function uses the average function...)<?phpfunction average(\$arr){    if (!count(\$arr)) return 0;    \$sum = 0;    for (\$i = 0; \$i < count(\$arr); \$i++)    {        \$sum += \$arr[\$i];    }    return \$sum / count(\$arr);}function variance(\$arr){    if (!count(\$arr)) return 0;    \$mean = average(\$arr);    \$sos = 0;    // Sum of squares    for (\$i = 0; \$i < count(\$arr); \$i++)    {        \$sos += (\$arr[\$i] - \$mean) * (\$arr[\$i] - \$mean);    }    return \$sos / (count(\$arr)-1);  // denominator = n-1; i.e. estimating based on sample                                     // n-1 is also what MS Excel takes by default in the                                    // VAR function}echo variance(array(4,6,23,15,18)); // echoes 64.7...correct value :)?> ```
-2
jordanolsommer at imap dot cc
15 years ago
``` The reason the bitwise AND ("&") operator works to determine whether a number is odd or even is because odd numbers expressed in binary always have the rightmost (2^0) bit = 1 and even numbers always have the 2^0 bit = 0. So if you do a " 1 & \$num", it will return zero if the number is even (since xxxxxxx0 [the even number in binary] and 00000001 [the 1]) don't share any bits, and will return 1 if the number is odd (xxxxxx1 and 000001).a clever way of doing things, but \$num % 2 would work as well i think :). ```
-3
tembenite at gmail dot com
12 years ago
``` To add to what Cornelius had, I have written a function that will take an array of numbers and return the least common multiple of them:function lcm_arr(\$items){    //Input: An Array of numbers    //Output: The LCM of the numbers    while(2 <= count(\$items)){        array_push(\$items, lcm(array_shift(\$items), array_shift(\$items)));    }    return reset(\$items);}//His Code below with \$'s added for varsfunction gcd(\$n, \$m) {   \$n=abs(\$n); \$m=abs(\$m);   if (\$n==0 and \$m==0)       return 1; //avoid infinite recursion   if (\$n==\$m and \$n>=1)       return \$n;   return \$m<\$n?gcd(\$n-\$m,\$n):gcd(\$n,\$m-\$n);}function lcm(\$n, \$m) {   return \$m * (\$n/gcd(\$n,\$m));} ```
-4
lummox
11 years ago
``` Wouldn't the following function do the same but a lot easier than the one in the comment before?function trimInteger(\$targetNumber,\$newLength) {    return \$targetNumber%pow(10,\$newLength); } ```
-3
Chronial "at" cyberpunkuniverse.de
15 years ago
``` Here are are a nPr and a nPc function(had to define NaN - don't know, how to this the "rigth" way)<?phpdefine (NaN,acos(1.01));function nCr(\$n,\$r){   if (\$r > \$n)      return NaN;   if ((\$n-\$r) < \$r)      return nCr(\$n,(\$n-\$r));   \$return = 1;   for (\$i=0;\$i < \$r;\$i++){      \$return *= (\$n-\$i)/(\$i+1);   }   return \$return;}function nPr(\$n,\$r){   if (\$r > \$n)      return NaN;   if (\$r)      return \$n*(nPr(\$n-1,\$r-1));   else      return 1;}?> ```
-4
marasek.SPAMLESS at telton.de
13 years ago
``` I could not resist to do a simpler version of the ordinal function:<?phpfunction ordinal(\$num){    \$num = (int)\$num;    \$digit = substr(\$num, -1, 1);    \$ord = "th";    switch(\$digit)    {        case 1: \$ord = "st"; break;        case 2: \$ord = "nd"; break;        case 3: \$ord = "rd"; break;    break;    }return \$num.\$ord;}?>One could replace the typecast with<?phpif(\$num===NULL or \$num===""){return NULL;}?>to get an empty result instead of "0th" in case \$num is empty too. ```
-2
ddarjany at yahoo dot com
11 years ago
``` Tim's fix of Evan's ordinal function causes another problem, it no longer works for number above 100.  (E.g. it returns 111st instead of 111th).  Here is a further modified version which should work for all numbers.<?PHPfunction ordinal(\$cardinal)    {  \$cardinal = (int)\$cardinal;  \$digit = substr(\$cardinal, -1, 1);  if (\$cardinal <100) \$tens = round(\$cardinal/10);  else \$tens = substr(\$cardinal, -2, 1);  if(\$tens == 1)  {    return \$cardinal.'th';  }  switch(\$digit) {    case 1:      return \$cardinal.'st';    case 2:      return \$cardinal.'nd';    case 3:      return \$cardinal.'rd';    default:      return \$cardinal.'th';  }} ?> ```
-2
16 years ago
``` Here is a cleaner factorial function:function factorial(\$s){    if(\$s) \$r = \$s * factorial(\$s - 1);    else \$r = 1;    return \$r;} ```
-2
jbeardsl at gte dot net
16 years ago
``` I needed a truncate function to operate on real numbers. I preferred not to use a string-manipulation method, so here's my solution. HTH...function truncate (\$num, \$digits = 0) {    //provide the real number, and the number of     //digits right of the decimal you want to keep.    \$shift = pow(10 , \$digits);    return ((floor(\$num * \$shift)) / \$shift);} ```
-4
twoscoopsofpig at NOSPAM dot gmail dot com
12 years ago
``` @ Moikboy:This may or may not be more simplified factorialization:<?php\$f=\$fact=25;while (\$fact>0){\$f=\$f*\$fact--;}echo \$f;?> ```
-4
graywh at gmail DELETE dot com
14 years ago
``` If you're really concerned about speed, you could compute the factorial of large numbers using the Gamma function of n-1.Integral y^(t-1)*Exp(-y) for y from 0 to InfinityFor Fibonacci numbers, there's a better-than-recursive way.((1+sqrt(5))/2)^(n/sqrt(5)) - ((1-sqrt(5))/2)^(n/sqrt(5)) ```
-4
chris at free-source dot com
15 years ago
``` to "convert" scientific notation to a float simply cast it:<?php\$val = '3.5e4';\$val = (float) \$val;echo \$val;?>output:35000 ```
-4
cornelius at skjoldhoej dot dk
18 years ago
``` I found that when dealing with tables, a 'least common multiple' function is sometimes useful for abusing tablespan and the likes. So here goes (you may choose to remove the first part of the gcd function if the function call is well-behaved): <?php function gcd(n, m) //greatest common divisor {     n=abs(n); m=abs(m);     if (n==0 and m==0)         return 1; //avoid infinite recursion     if (n==m and n>=1)         return n;     return m<n?gcd(n-m,n):gcd(n,m-n); } function lcm(n, m) //least common multiple {     return m*(n/gcd(n,m)); } ?> This may or may not be something to consider adding to the mathematical function library. ```
-7
eric at woolhiser dot com
14 years ago
``` For all you guys writing mortgage calculators out there:<?phpfunction payment(\$apr,\$n,\$pv,\$fv=0.0,\$prec=2){    /* Calculates the monthly payment rouned to the nearest penny    ** \$apr = the annual percentage rate of the loan.    ** \$n   = number of monthly payments (360 for a 30year loan)    ** \$pv    = present value or principal of the loan    ** \$fv  = future value of the loan    ** \$prec = the precision you wish rounded to    */    /****************************************\    ** No Warranty is expressed or implied. **    *****************************************/        if (\$apr !=0) {        \$alpha = 1/(1+\$apr/12);        \$retval =  round(\$pv * (1 - \$alpha) / \$alpha /         (1 - pow(\$alpha,\$n)),\$prec) ;    } else {        \$retval = round(\$pv / \$n, \$prec);    }    return(\$retval);}?> ```
-4
erikvandeven100 at gmail dot com
2 years ago
``` This is my factorial method<?phpfunction factorial(\$nr){    \$product = array_product(range(1,++\$nr));    return \$product / \$nr;}?>It uses the reversed method by applying division instead of multiplication, so it even returns the right answer when entering 0. ```
-5
jos at gtacrime dot nl
13 years ago
``` Thanks to Chronial "at" cyberpunkuniverse.de, I was able to create the binompdf(n, p, k) function.<?phpfunction nCr(\$n, \$k){   if (\$k > \$n)     return NaN;   if ((\$n - \$k) < \$k)     return nCr(\$n, (\$n - \$k));   \$return = 1;   for (\$i=0; \$i<\$k; \$i++){     \$return *= (\$n - \$i) / (\$i + 1);   }   return \$return;} function binompdf(\$n, \$p, \$k){    \$return = nCr(\$n, \$k) * pow(\$p, \$k) * pow((1 - \$p), (\$n - \$k));    return \$return;}?> ```
-5
donnieb819 at hotmail dot NOSPAM dot com
14 years ago
``` Method to convert an arbitrary decimal number to its most reduced fraction form (so a string is returned, this method would probably be used for output formatting purposes.)  There were other methods similar to this one on the page, but none did quite what I wanted.  It's maybe not the most elegant code, but it gets the job done.  Hope this helps someone.  An iterative form of Euclid's algorithm is used to find the GCD.<?phpfunction dec2frac( \$decimal ){  \$decimal = (string)\$decimal;  \$num = '';  \$den = 1;  \$dec = false;    // find least reduced fractional form of number  for( \$i = 0, \$ix = strlen( \$decimal ); \$i < \$ix; \$i++ )  {    // build the denominator as we 'shift' the decimal to the right    if( \$dec ) \$den *= 10;        // find the decimal place/ build the numberator    if( \$decimal{\$i} == '.' ) \$dec = true;    else \$num .= \$decimal{\$i};  }  \$num = (int)\$num;      // whole number, just return it  if( \$den == 1 ) return \$num;      \$num2 = \$num;  \$den2 = \$den;  \$rem  = 1;  // Euclid's Algorithm (to find the gcd)  while( \$num2 % \$den2 ) {    \$rem = \$num2 % \$den2;    \$num2 = \$den2;    \$den2 = \$rem;  }  if( \$den2 != \$den ) \$rem = \$den2;      // now \$rem holds the gcd of the numerator and denominator of our fraction  return (\$num / \$rem ) . "/" . (\$den / \$rem);}?>Examples:echo dec2frac( 10 );echo dec2frac( .5 );echo dec2frac( 5.25 );echo dec2frac( .333333333 );yields:101/221/4333333333/1000000000 ```
-4
tim at durge dot org
12 years ago
``` In Evan's ordinal function, the line:<?php  \$tens = substr(\$cardinal, -2, 1);?>needs to be replaced by:<?php  \$tens = round(\$cardinal/10);?>or similar. At least on PHP 4.3.10,  substr("1", -2, 1)  returns '1' - so Evan's function gives "1th", as well as "11th".  This is contrary to the documentation, but is noted in the comments on the substr manual page. ```
-4
ausvald at tut dot by
15 years ago
``` I see there are some factorial functions below.I'll provide the best one:<?function factorial(\$n){ \$n=(int)\$n;  \$f=1;  for(;\$n>0;--\$n) \$f*=\$n;  return \$f;}?> ```
-5
rubo77 at spacetrace dot org
10 years ago
``` <?php function lcd(\$n,\$m, \$maxvarianzpercent=0){    // set \$maxvarianzpercent=5 to get a small, but approx. result    /* a better lcd function with varianz:    for example use     lcd(141,180,5) to get the approx. lcd '7/9' which is in fact 140/180    */    // ATTENTION!!! can be really slow if \$m is >1000        \$d=\$n/\$m;    \$f=1;    while(\$d*\$f!=intval(\$d*\$f)){        \$f++;    }    \$r=(\$d*\$f).'/'.\$f;    if((\$d*\$f)<=10 or \$f<=10) return \$r;    else if(\$maxvarianzpercent>0){        \$f=1;        while(\$d*\$f!=intval(\$d*\$f) and (\$d*\$f)-intval(\$d*\$f) > \$maxvarianzpercent/100){            \$f++;        }        return intval(\$d*\$f).'/'.\$f;    } else return \$r;}?> ```
-5
Evan Broder
12 years ago
``` A slightly more complex but much more accurate cardinal=>ordinal function (the one below doesn't account for 11th, 12th, and 13th, which don't follow the usual rules):<?php    function ordinal(\$cardinal)    {        \$cardinal = (int)\$cardinal;        \$digit = substr(\$cardinal, -1, 1);        \$tens = substr(\$cardinal, -2, 1);        if(\$tens == 1)        {            return \$cardinal.'th';        }                switch(\$digit)        {        case 1:            return \$cardinal.'st';        case 2:            return \$cardinal.'nd';        case 3:            return \$cardinal.'rd';        default:            return \$cardinal.'th';        }    }?> ```
-5
shanx at shanx dot com
16 years ago
``` <?/** * Function to calculate base36 values from a number. Very * useful if you wish to generate IDs from numbers. * * @param \$value The number * @param \$base The base to be applied (16, 36 or 64) * @return The calculated string * @author Shashank Tripathi (shanx@shanx.com) * @version 0.1 - Let me know if something doesnt work * */ function base36(\$value, \$base) {    \$baseChars = array('0', '1', '2', '3', '4', '5',                       '6', '7', '8', '9', 'a', 'b',                       'c', 'd', 'e', 'f', 'g', 'h',                       'i', 'j', 'k', 'l', 'm', 'n',                       'o', 'p', 'q', 'r', 's', 't',                       'u', 'v', 'w', 'x', 'y', 'z'                     );    \$remainder = 0;    \$newval = "";        while ( \$value > 0 )     {        \$remainder = \$value % \$base;        \$value = ( (\$value - \$remainder)/ \$base );        \$newval .= \$baseChars[\$remainder];    }    return strrev(\$newval);    }echo "The string for 46655, for instance, is " . base36(46655, 36);?> ```
-7
webkid%webkid.com
17 years ago
``` I found it kind of irritating that PHP had no native functionality for a calculating Factorials. Since I really didn't feel like loading the GMP library, I figured I'd write my own function.function fact(\$s){\$r=(int)\$s; for (\$i=\$r;\$i--;\$i>1){\$r=\$r*\$i;} return \$r;}I think that's right... I havn't tested it extensively but it should work. ```