CascadiaPHP 2024

bindec

(PHP 4, PHP 5, PHP 7, PHP 8)

bindec二进制转换为十进制

说明

bindec(string $binary_string): int|float

返回 binary_string 参数所表示的二进制数的十进制等价值。

bindec() 将一个二进制数转换成 int,或者出于大小的需要,转换为 float 类型。

bindec() 将所有的 binary_string 值解释为无符号整数。这是由于 bindec() 函数将其最高有效位视为数量级而非符号位。

参数

binary_string

要转换的二进制字符串。binary_string 中的任何无效字符都会默认忽略。自 PHP 7.4.0 起,弃用使用任何无效字符。

警告

参数必须为字符串。使用其他数据类型会导致不可预知的结果。

返回值

binary_string 的十进制数值

更新日志

版本 说明
7.4.0 传递任何无效字符现在将生成弃用通知。但仍会计算结果,就好像无效字符不存在一样。

示例

示例 #1 bindec() 示例

<?php
echo bindec('110011') . "\n";
echo
bindec('000110011') . "\n";

echo
bindec('111');
?>

以上示例会输出:

51
51
7

示例 #2 bindec() 将输入解读为无符号整数

<?php
/*
* The lesson from this example is in the output
* rather than the PHP code itself.
*/

$magnitude_lower = pow(2, (PHP_INT_SIZE * 8) - 2);
p($magnitude_lower - 1);
p($magnitude_lower, 'See the rollover? Watch it next time around...');

p(PHP_INT_MAX, 'PHP_INT_MAX');
p(~PHP_INT_MAX, 'interpreted to be one more than PHP_INT_MAX');

if (
PHP_INT_SIZE == 4) {
$note = 'interpreted to be the largest unsigned integer';
} else {
$note = 'interpreted to be the largest unsigned integer
(18446744073709551615) but skewed by float precision'
;
}
p(-1, $note);


function
p($input, $note = '') {
echo
"input: $input\n";

$format = '%0' . (PHP_INT_SIZE * 8) . 'b';
$bin = sprintf($format, $input);
echo
"binary: $bin\n";

ini_set('precision', 20); // For readability on 64 bit boxes.
$dec = bindec($bin);
echo
'bindec(): ' . $dec . "\n";

if (
$note) {
echo
"NOTE: $note\n";
}

echo
"\n";
}
?>

以上示例在 32 位机器上的输出:

input:        1073741823
binary:       00111111111111111111111111111111
bindec():     1073741823

input:        1073741824
binary:       01000000000000000000000000000000
bindec():     1073741824
NOTE:         See the rollover?  Watch it next time around...

input:        2147483647
binary:       01111111111111111111111111111111
bindec():     2147483647
NOTE:         PHP_INT_MAX

input:        -2147483648
binary:       10000000000000000000000000000000
bindec():     2147483648
NOTE:         interpreted to be one more than PHP_INT_MAX

input:        -1
binary:       11111111111111111111111111111111
bindec():     4294967295
NOTE:         interpreted to be the largest unsigned integer

以上示例在 64 位机器上的输出:

input:        4611686018427387903
binary:       0011111111111111111111111111111111111111111111111111111111111111
bindec():     4611686018427387903

input:        4611686018427387904
binary:       0100000000000000000000000000000000000000000000000000000000000000
bindec():     4611686018427387904
NOTE:         See the rollover?  Watch it next time around...

input:        9223372036854775807
binary:       0111111111111111111111111111111111111111111111111111111111111111
bindec():     9223372036854775807
NOTE:         PHP_INT_MAX

input:        -9223372036854775808
binary:       1000000000000000000000000000000000000000000000000000000000000000
bindec():     9223372036854775808
NOTE:         interpreted to be one more than PHP_INT_MAX

input:        -1
binary:       1111111111111111111111111111111111111111111111111111111111111111
bindec():     18446744073709551616
NOTE:         interpreted to be the largest unsigned integer
              (18446744073709551615) but skewed by float precision

注释

注意:

此函数可以将太大的数字转换为适应平台的 int 类型,在这种情况下,较大值将会作为 float 返回。

参见

add a note

User Contributed Notes 10 notes

up
7
info at rickdg dot nl
14 years ago
Two functions to convert 16bit or 8bit binary to integer using two's complement. If input exceeds maximum bits, false is returned. Function is easily scalable to x bits by changing the hexadecimals.

<?php function _bin16dec($bin) {
// Function to convert 16bit binary numbers to integers using two's complement
$num = bindec($bin);
if(
$num > 0xFFFF) { return false; }
if(
$num >= 0x8000) {
return -((
$num ^ 0xFFFF)+1);
} else {
return
$num;
}
}

function
_bin8dec($bin) {
// Function to convert 8bit binary numbers to integers using two's complement
$num = bindec($bin);
if(
$num > 0xFF) { return false; }
if(
$num >= 0x80) {
return -((
$num ^ 0xFF)+1);
} else {
return
$num;
}
}
?>
up
3
martin at punix dot de
21 years ago
## calculate binary with "shift-method" ##

<?php
function dec2bin($decimal_code){
for(
$half=($decimal_code);$half>=1;$half=(floor($half))/2){
if((
$half%2)!=0){
$y.=1;
}
else{
$y.=0;
}
}
$calculated_bin=strrev($y);
return
$calculated_bin;
}
?>

## example ##

[bin] 123 = [dec] 1111011

e.g.
123/2 = 61,5 => 1
61/2 = 30,5 => 1
30/2 = 15 => 0
15/2 = 7,5 => 1
7/2 = 3,5 => 1
3/2 = 1,5 => 1
1/2 = 0,5 => 1
(0/2 = 0 finish)
up
3
gwbdome at freenet dot de
19 years ago
i think a better method than the "shift-method" is my method ^^...
here it comes:

function convert2bin($string) {
$finished=0;
$base=1;
if(preg_match("/[^0-9]/", $string)) {
for($i=0; $string!=chr($i); $i++);
$dec_nr=$i;
}
else $dec_nr=$string;
while($dec_nr>$base) {
$base=$base*2;
if($base>$dec_nr) {
$base=$base/2;
break;
}
}
while(!$finished) {
if(($dec_nr-$base)>0) {
$dec_nr=$dec_nr-$base;
$bin_nr.=1;
$base=$base/2;
}
elseif(($dec_nr-$base)<0) {
$bin_nr.=0;
$base=$base/2;
}
elseif(($dec_nr-$base)==0) {
$bin_nr.=1;
$finished=1;
while($base>1) {
$bin_nr.=0;
$base=$base/2;
}
}
}
return $bin_nr;
}

=====================================================

if you want to reconvert it (from binary to string or integer) you can use this function:

function reconvert($bin_nr) {
$base=1;
$dec_nr=0;
$bin_nr=explode(",", preg_replace("/(.*),/", "$1", str_replace("1", "1,", str_replace("0", "0,", $bin_nr))));
for($i=1; $i<count($bin_nr); $i++) $base=$base*2;
foreach($bin_nr as $key=>$bin_nr_bit) {
if($bin_nr_bit==1) {
$dec_nr+=$base;
$base=$base/2;
}
if($bin_nr_bit==0) $base=$base/2;
}
return(array("string"=>chr($dec_nr), "int"=>$dec_nr));
}
up
2
Nitrogen
15 years ago
Binary to Decimal conversion using the BCMath extension..

<?php

function BCBin2Dec($Input='') {
$Output='0';
if(
preg_match("/^[01]+$/",$Input)) {
for(
$i=0;$i<strlen($Input);$i++)
$Output=BCAdd(BCMul($Output,'2'),$Input{$i});
}
return(
$Output);
}

?>

This will simply convert from Base-2 to Base-10 using BCMath (arbitrary precision calculation).

See also: my 'BCDec2Bin' function on the 'decbin' document.
Enjoy,
Nitrogen.
up
1
alan hogan dot com slash contact
16 years ago
The "smartbindec" function I wrote below will convert any binary string (of a reasonable size) to decimal. It will use two's complement if the leftmost bit is 1, regardless of bit length. If you are getting unexpected negative answers, try zero-padding your strings with sprintf("%032s", $yourBitString).

<?php
function twoscomp($bin) {
$out = "";
$mode = "init";
for(
$x = strlen($bin)-1; $x >= 0; $x--) {
if (
$mode != "init")
$out = ($bin[$x] == "0" ? "1" : "0").$out;
else {
if(
$bin[$x] == "1") {
$out = "1".$out;
$mode = "invert";
}
else
$out = "0".$out;
}
}
return
$out;
}
function
smartbindec($bin) {
if(
$bin[0] == 1)
return -
1 * bindec(twoscomp($bin));
else return (int)
bindec($bin);
}
?>
up
0
patrick dot boens at latosensu dot be
12 years ago
Left-shift a string by a number of bytes
<?php
function STR_shl( $szStr,$nBits )
/*-----------------------------*/
{
if (
$nBits < 1 || $nBits > 7 ) /* If not adequate number of bits */
{
return (
$szStr ); /* Return the original string */
} /* if ( $nBits < 1 || $nBits > 7 ) */

if ( ( $iLength = strlen( $szStr ) ) <= 0 ) /* If string empty */
{
return (
$szStr ); /* Return the original string */
} /* if ( ( $iLength = strlen( $szStr ) ) <= 0 ) */

$szRetVal = ''; /* Create an empty string */

$szBits = STR_Binary( $szStr ); /* $szStr in bits */
$szLostBits = STR_Left( $szBits,$nBits ); /* The $nBits leftmost bits of the string */
$szShifted = substr( $szBits,$nBits ) . $szLostBits; /* $szStr left shifted */

for ( $i = 0;$i < $iLength;$i++ ) /* Treat the entire string (per slice of 8 bits) */
{
$szRetVal .= chr( bindec( substr( $szShifted,$i * 8,8 ) ) ); /* Concatenate the CHR to the result string */
} /* for ( $i = 0;$i < $iLength;$i++ ) */

return ( $szRetVal ); /* Return result to caller */
}
?>

Right-shift a string by a number of bytes
<?php

function STR_shr( $szStr,$nBits )
/*-----------------------------*/
{
if (
$nBits < 1 || $nBits > 7 ) /* If not adequate number of bits */
{
return (
$szStr ); /* Return the original string */
} /* if ( $nBits < 1 || $nBits > 7 ) */

if ( ( $iLength = strlen( $szStr ) ) <= 0 ) /* If string empty */
{
return (
$szStr ); /* Return the original string */
} /* if ( ( $iLength = strlen( $szStr ) ) <= 0 ) */

$szRetVal = ''; /* Create an empty string */

$szBits = STR_Binary( $szStr ); /* $szStr in bits */
$szLostBits = STR_Right( $szBits,$nBits ); /* The $nBits rightmost bits of the string */
$szShifted = $szLostBits . substr( $szBits,0,-$nBits ); /* $szStr right shifted */

for ( $i = 0;$i < $iLength;$i++ ) /* Treat the entire string (per slice of 8 bits) */
{
$szRetVal .= chr( bindec( substr( $szShifted,$i * 8,8 ) ) ); /* Concatenate the CHR to the result string */
} /* for ( $i = 0;$i < $iLength;$i++ ) */

return ( $szRetVal ); /* Return result to caller */
}
?>

Additional functions used by the two preceding:
<?php
function STR_Binary( $szStr )
/*-------------------------*/
{
$szRetVal = ''; /* Ready to return an empty string */

if ( ( $iLength = strlen( $szStr ) ) > 0 ) /* If string NOT empty */
{
for (
$i = 0; $i < $iLength;$i++ ) /* Treat each character of the string */
{
$szRetVal .= sprintf( '%08b',ord( $szStr[$i] ) ); /* Turn this char to a binary representation (8 bits) */
} /* for ( $i = 0; $i < $iLength;$i++ ) */
} /* if ( ( $iLength = strlen( $szStr ) ) > 0 ) */

return ( $szRetVal ); /* Return result to caller */
}

function
STR_Left( $szStr,$iCount = 1 )
/*----------------------------------*/
{
return
substr( $szStr,0,$iCount );
}
/* End of function strleft() */

function STR_Right( $szString,$iCount )
/*----------------------------------*/
{
return
substr( $szString,0 + strlen( $szString ) - $iCount,$iCount );
}
?>
up
-1
mashematician at gmail dot com
16 years ago
A binary to decimal conversion function that takes advantage of the BC library functions to return decimal values of arbitrary length.

Input type must be a string in order to work properly.

<?php

function binary_to_decimal($a) {
$bin_array = str_split($a);

$y=sizeof($bin_array)-1;
for (
$x=0; $x<sizeof($bin_array)-1; $x++) {
if (
$bin_array[$x] == 1) {
$bin_array[$x] = bcpow(2, $y);
}
$y--;
}

for (
$z=0; $z<sizeof($bin_array); $z++) {
$result = bcadd($result, $bin_array[$z]);
}
echo
$result;
}

binary_to_decimal('11111');

?>
up
-1
jpfstange at gmail dot com
8 years ago
<?php

//binfloat (For single precision floating point numbers)
//IEE754
//https://en.wikipedia.org/wiki/Single-precision_floating-point_format

function binfloat(Array $num){

$sign = $num[0] ? 1 : -1; //1 bit
$exponent = pow(2,bindec(implode('',array_slice($num,1,8)))-127);
$fraction = array_slice($num,9,count($num)); //23 bits
$fracSum = 1;

for(
$i=0;$i<23;$i++){

$fracSum += $fraction[$i] * pow(2,-1-$i);

}

return
$fracSum*$exponent;

}

$num = isset($_GET['num']) ? $_GET['num'] : '00111110001000000000000000000000';

if(
strlen($num)<32){

echo
"Invalid binary number $num\n";
exit(
1);

}

$num = str_split($num);

echo
sprintf('Num is: [%s]%s',implode('',$num),"\n");
echo
sprintf('Result is: %s%s',binfloat($num),"\n");
up
-1
flashpack at gmail dot com
15 years ago
for converting fractions :
eg : 1001.1101

<?php
function BinaryToDecimal($binary){
$binary=trim($binary);
if (
strstr($binary,'.')){
$split=explode('.',$binary);
$integer=$split[0];
$fraction=$split[1];

$digits=str_split($fraction);
$num=sizeof($digits);
for (
$i=1; $i<=$num;$i++){
if (
$digits[$i-1]>1){
echo
'<script>alert("Enter Binary Digits Only {0,1}\n \n eg: 11001 or 11001.011");history.go(-1)</script> ';
}
$exponent=pow(2,-$i);
$fraction_result+=$digits[$i-1]*$exponent;
}

}else{
$integer=$binary;
}

$splits=str_split($integer);
$num=sizeof($splits)-1;
$i=$num;
foreach(
$splits as $digits){
if (
$digits>1){
echo
'<script>alert("Enter Binary Digits Only {0,1}\n \n eg: 11001 or 11001.011");history.go(-1)</script> ';
}
$exponent=pow(2,$i);
$integer_result+=$digits*$exponent;
$i--;
}
if(
$fraction_result){
$result=$integer_result+$fraction_result;
}else {
$result=$integer_result;
}
return
$result ;
}
?>
up
-3
nodarinodo at mail dot ru
15 years ago
<?php
// bindecfunc :)))) I think it works well too :)
function bindecc($str)
{
$str = str_replace(" ", "", $str);
$strr = preg_match('/[^01]/', $str);
if(
$strr == 1) { return "<b> Error ! only 1 and 0;</b>"; }
$strsig = strlen($str);
$strr1 = strrev($str);
$strf = '';
for(
$i = $strsig; $i >= 0; $i--)
{
$strf += ($strr1[$i] * pow(2, $i));
#$strf += $str[$i];
}
return
$strf;
}
?>
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