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## Integer 整型

### 语法

Example #1 整数文字表达

``` <?php\$a = 1234; // 十进制数\$a = -123; // 负数\$a = 0123; // 八进制数 (等于十进制 83)\$a = 0x1A; // 十六进制数 (等于十进制 26)?> ```

```decimal     : [1-9][0-9]*
| 0

octal       : 0[0-7]+

binary      : 0b[01]+

integer     : [+-]?decimal
| [+-]?octal
| [+-]?binary
```

Warning

Example #2 八进制数的怪事

``` <?phpvar_dump(01090); // 八进制 010 = 十进制 8?> ```

### 整数溢出

Example #3 32 位系统下的整数溢出

``` <?php\$large_number = 2147483647;var_dump(\$large_number);                     // int(2147483647)\$large_number = 2147483648;var_dump(\$large_number);                     // float(2147483648)\$million = 1000000;\$large_number =  50000 * \$million;var_dump(\$large_number);                     // float(50000000000)?> ```

Example #4 64 位系统下的整数溢出

``` <?php\$large_number = 9223372036854775807;var_dump(\$large_number);                     // int(9223372036854775807)\$large_number = 9223372036854775808;var_dump(\$large_number);                     // float(9.2233720368548E+18)\$million = 1000000;\$large_number =  50000000000000 * \$million;var_dump(\$large_number);                     // float(5.0E+19)?> ```

PHP 中没有整除的运算符。1/2 产生出 float 0.5。值可以舍弃小数部分强制转换为 integer，或者使用 round() 函数可以更好地进行四舍五入。

``` <?phpvar_dump(25/7);         // float(3.5714285714286) var_dump((int) (25/7)); // int(3)var_dump(round(25/7));  // float(4) ?> ```

### 转换为整型

#### 从布尔值转换

`FALSE` 将产生出 0（零），`TRUE` 将产生出 1（壹）。

#### 从浮点型转换

Warning

``` <?phpecho (int) ( (0.1+0.7) * 10 ); // 显示 7!?> ```

Caution

### User Contributed Notes 21 notes

16
Paul
6 years ago
``` "always round it downwards" It seems to truncate, or round toward zero, rather than downward. If the float is negative, it is rounded up. ```
14
rustamabd@gmail-you-know-what
6 years ago
``` Be careful with using the modulo operation on big numbers, it will cast a float argument to an int and may return wrong results. For example: <?php     \$i = 6887129852;     echo "i=\$i\n";     echo "i%36=".(\$i%36)."\n";     echo "alternative i%36=".(\$i-floor(\$i/36)*36)."\n"; ?> Will output: i=6.88713E+009 i%36=-24 alternative i%36=20 ```
12
d_n at NOSPAM dot Loryx dot com
6 years ago
``` Here are some tricks to convert from a "dotted" IP address to a LONG int, and backwards. This is very useful because accessing an IP addy in a database table is very much faster if it's stored as a BIGINT rather than in characters. IP to BIGINT: <?php   \$ipArr    = explode('.',\$_SERVER['REMOTE_ADDR']);   \$ip       = \$ipArr[0] * 0x1000000             + \$ipArr[1] * 0x10000             + \$ipArr[2] * 0x100             + \$ipArr[3]             ; ?> IP as BIGINT read from db back to dotted form: Keep in mind, PHP integer operators are INTEGER -- not long. Also, since there is no integer divide in PHP, we save a couple of S-L-O-W floor (<division>)'s by doing bitshifts. We must use floor(/) for \$ipArr[0] because though \$ipVal is stored as a long value, \$ipVal >> 24 will operate on a truncated, integer value of \$ipVal! \$ipVint is, however, a nice integer, so we can enjoy the bitshifts. <?php         \$ipVal = \$row['client_IP'];         \$ipArr = array(0 =>                     floor(  \$ipVal               / 0x1000000) );         \$ipVint   = \$ipVal-(\$ipArr[0]*0x1000000); // for clarity         \$ipArr[1] = (\$ipVint & 0xFF0000)  >> 16;         \$ipArr[2] = (\$ipVint & 0xFF00  )  >> 8;         \$ipArr[3] =  \$ipVint & 0xFF;         \$ipDotted = implode('.', \$ipArr); ?> ```
Anonymous
9 years ago
``` Sometimes you need to parse an unsigned 32 bit integer. Here's a function I 've used:                                                                                     function parse_unsigned_int(\$string) {         \$x = (float)\$string;         if (\$x > (float)2147483647)             \$x -= (float)"4294967296";         return (int)\$x;     } ```
Anonymous
6 years ago
``` To force the correct usage of 32-bit unsigned integer in some functions, just add '+0'  just before processing them. for example echo(dechex("2724838310")); will print '7FFFFFFF' but it should print 'A269BBA6' When adding '+0' php will handle the 32bit unsigned integer correctly echo(dechex("2724838310"+0)); will print 'A269BBA6' ```
pere dot cil at wanadoo dot fr
2 years ago
``` Please also note that the maximum stored in the integer depends on the platform / compilation; on windows xp 32 bits, the following value: 0x5468792130ABCDEF echoes to: 6.0822444802213E+18 (cast to float) On a fully 64 bits system, it echoes to: 6082244480221302255 ```
wbcarts at juno dot com
5 years ago
``` PHP offers a slew of built-in functions and automatic type-casting routines which can get pretty complicated. But most of the time, you still have to take matters into your own hands and allow PHP to do its thing. In that case, and something that has NOT been mentioned, is how to construct your code. To keep things simple, I divide all my scripts in half. The top half gives my scripts the "capability" they need, and the lower half is the actual code to be "run" or "executed". <?php /*  * build the program's capability - define variables and functions...  */ \$item_label = '';        // type string \$item_price = 0.0;       // type float \$item_qty = 1;           // type integer \$item_total = 0.0;       // type float - to set use calculate() function calculate(){   global \$item_price, \$item_qty, \$item_total;   \$item_price = number_format(\$item_price, 2);   \$item_total = number_format((\$item_price * \$item_qty), 2); } function itemToString() {   global \$item_label, \$item_price, \$item_qty, \$item_total;   return "\$item_label [price=\\$\$item_price, qty=\$item_qty, total=\\$\$item_total]"; } /*  * run the program - set data, call methods...  */ \$item_label = "Coffee"; \$item_price = 3.89; \$item_qty = 2; calculate();           // set \$item_total echo itemToString();   // -> Coffee [price=\$3.89, qty=2, total=\$7.78] \$item_label = "Chicken"; \$item_price = .80;     // per lb. \$item_qty = 3.5;       // lbs. calculate();           // set \$item_total echo itemToString();   // -> Chicken [price=\$0.80, qty=3.5, total=\$2.80] ?> Note: All type-casting is done by PHP's built-in number_format() method. This allows our program to enter any number (float or int) on item price or quantity in the runtime part of our script. Also, if we explicitly cast values to integer in the capability part of our script, then we start getting results that may not be desirable for this program. For example, if in the calculate method we cast item_qty to integer, then we can no longer sell chicken by the pound! ```
iletras at yahoo dot com
3 years ago
``` //This is a (simpler ?) function to return number of digits of an integer. //function declaration function count_digit(\$number) {   return  strlen((string) \$number); } //function call \$num = 12312; \$number_of_digits = count_digit(\$num); //this is call :) echo \$number_of_digits; //prints 5 ```
Hamza Burak Ylmaz
5 years ago
``` <?php //This is a simple function to return number of digits of an integer. //function declaration function count_digit(\$number) {     \$digit = 0;     do     {         \$number /= 10;      //\$number = \$number / 10;         \$number = intval(\$number);         \$digit++;        }while(\$number!=0);     return \$digit; } //function call \$num = 12312; \$number_of_digits = count_digit(\$num); //this is call :) echo \$number_of_digits; //prints 5 ?> ```
popefelix at gmail dot com
6 years ago
``` Be careful when using integer conversion to test something to see if it evaluates to a positive integer or not.  You might get unexpected behaviour. To wit: <?php error_reporting(E_ALL); require_once 'Date.php'; \$date = new Date(); print "\\$date is an instance of " . get_class(\$date) . "\n"; \$date += 0; print "\\$date is now \$date\n"; var_dump(\$date); \$foo = new foo(); print "\\$foo is an instance of " . get_class(\$foo) . "\n"; \$foo += 0; print "\\$foo is now \$foo\n"; var_dump(\$foo); class foo {     var \$bar = 0;     var \$baz = "la lal la";     var \$bak;     function foo() {         \$bak = 3.14159;     } } ?> After the integer conversion, you might expect both \$foo and \$date to evaluate to 0.  However, this is not the case: \$date is an instance of Date Notice: Object of class Date could not be converted to int in /home/kpeters/work/sketches/ObjectSketch.php on line 7 \$date is now 1 int(1) \$foo is an instance of foo Notice: Object of class foo could not be converted to int in /home/kpeters/work/sketches/ObjectSketch.php on line 13 \$foo is now 1 int(1) This is because the objects are first converted to boolean before being converted to int. ```
Jacek
6 years ago
``` On 64 bits machines max integer value is 0x7fffffffffffffff (9 223 372 036 854 775 807). ```
jmw254 at cornell dot edu
7 years ago
``` Try this one instead: function iplongtostring(\$ip) {     \$ip=floatval(\$ip); // otherwise it is capped at 127.255.255.255     \$a=(\$ip>>24)&255;     \$b=(\$ip>>16)&255;     \$c=(\$ip>>8)&255;     \$d=\$ip&255;     return "\$a.\$b.\$c.\$d"; } ```
php at richardneill dot org
9 months ago
``` A leading zero in a numeric literal means "this is octal". But don't be confused: a leading zero in a string does not. Thus: \$x = 0123;          // 83 \$y = "0123" + 0     // 123 ```
darkshire
6 years ago
``` d_n at NOSPAM dot Loryx dot com 13-Aug-2007 05:33 Here are some tricks to convert from a "dotted" IP address to a LONG int, and backwards. This is very useful because accessing an IP addy in a database table is very much faster if it's stored as a BIGINT rather than in characters. IP to BIGINT: <?php   \$ipArr    = explode('.',\$_SERVER['REMOTE_ADDR']);   \$ip       = \$ipArr[0] * 0x1000000             + \$ipArr[1] * 0x10000             + \$ipArr[2] * 0x100             + \$ipArr[3]             ; ?> This can be written in a bit more efficient way: <?php   \$ipArr    = explode('.',\$_SERVER['REMOTE_ADDR']);   \$ip       = \$ipArr[0]<<24             + \$ipArr[1]<<16             + \$ipArr[2] <<8             + \$ipArr[3]             ; ?> shift is more cheaper. ```
rickard_cedergren at yahoo dot com
8 years ago
``` When doing large subtractions on 32 bit unsigned integers the result sometimes end up negative. My example script converts a IPv4 address represented as a 32 bit unsigned integer to a dotted quad (similar to ip2long()), and adds a "fix" to the operation.    /**************************     * int_oct(\$ip)     * Convert INTeger rep of IP to octal (dotted quad)     */    function int_oct(\$ip) {       /* Set variable to float */       settype(\$ip, float);       /* FIX for silly PHP integer syndrome */       \$fix = 0;       if(\$ip > 2147483647) \$fix = 16777216;       if(is_numeric(\$ip)) {          return(sprintf("%u.%u.%u.%u",                 \$ip / 16777216,                 ((\$ip % 16777216) + \$fix) / 65536,                 ((\$ip % 65536) + \$fix / 256) / 256,                 (\$ip % 256) + \$fix / 256 / 256                 )      );       }       else {          return('');       }    } ```
-3
eric
5 years ago
``` In response to the comment by me at troyswanson dot net: -2147483648 falls into the range of 32 bit signed integers yet php treats it as a float.  However, -2147483647-1 is treated as an integer. The following code demonstrates: <?php     var_dump(-2147483648); //float(-2147483648)     var_dump(-2147483647 - 1); //int(-2147483648) ?> This is probably very similar to the MS C bug which also treats -2147483648 as an UNSIGNED because it thinks it's out of the range of a signed int. The problem is that the parser does not view "-x" as a single token, but rather as two, "-" and "x".  Since "x" is out of the range of an INT, it is promoted to float, even though in this unique case, "-x" is in the range of an int. The best cure is probably to replace "-2147483648" with "0x80000000", as that is the hexadecimal equivalent of the same number. Hope that helps explain what's going on Peace  - Eric / fez ```
-6
winterheat
5 years ago
``` PHP_INT_SIZE seems to be 8 when it is 64 bit integers... so 8 means the number of bytes, or number of 8-bits. ```
-7
php at keith tyler dot com
2 years ago
``` If you need to convert a numeric string (or more to the point, an object that represents a numeric value) that is greater then PHP_INT_MAX, and you don't have GMP or BCMath installed, you can cast to float. For example, when using SimpleXMLElement, you sometimes have to cast the extracted values, such as xml attributes, because they are returned as SimpleXMLElements and not their values' native types. While print() has no trouble with converting them, other functions, such as max(), might not. But if you cast such a value with (int), and it is over PHP_INT_MAX, you will just get PHP_INT_MAX (and vice versa for negative numbers). The Q&D no-muss solution is to cast to (float) instead. ```
-9
autotelic at NOOOOSPAM dot hotmail dot com
6 years ago
``` A note about converting IP addresses for storage in database.  For MySQL, this is unnecessary as it has built in support via the INET functions.  Also, there is no need to use BIGINT.  UNSIGNED INT is, at 4 bytes, the perfect size for holding an IP (column must be defined as UNSIGNED).  This can basically halve the storage size, as BIGINT is an 8 byte data type. INET_ATON() converts a dotted IP string to INT: INSERT table(ip) VALUES(INET_ATON('127.0.0.1')); INET_NTOA() converts an INT to dotted IP string: SELECT INET_NTOA(ip) FROM table returns '127.0.0.1' Details: http://dev.mysql.com/doc/refman/5.1/en/miscellaneous-functions.html ```
-10
sean dot gilbertson at gmail dot com
4 years ago
``` You can make a signed, negative integer an unsigned integer (in string form) by doing the following: <?php \$unsigned = sprintf('%u', -5); echo \$unsigned; // prints 4294967291 ?> ```
-10
Richard
2 years ago
``` Integer arithmetic in PHP is more accurate than one might think. On a 32-bit system, the largest value that can be held in an INT is  2147483647. However, a FLOAT can accurately hold integer values up to 10000000000000. (this is because the significand precision of a double is 53-bits). ```