Math 函数
PHP Manual

bindec

(PHP 4, PHP 5)

bindec二进制转换为十进制

说明

number bindec ( string $binary_string )

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 integer。可转换的最大的数为 31 位 1 或者说十进制的 2147483647。PHP 4.1.0 开始,该函数可以处理大数值,这种情况下,它会返回 float 类型。

参数

binary_string

The binary string to convert

Warning

The parameter must be a string. Using other data types will produce unexpected results.

返回值

The decimal value of binary_string

更新日志

版本 说明
4.1.0 The function can now convert numbers that are too large to fit into the platforms integer type, larger values are returned as float in that case.

范例

Example #1 bindec() 例子

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

echo 
bindec('111');
?>

以上例程会输出:

51
51
7

Example #2 bindec() interprets input as unsigned integers

<?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";
}
?>

以上例程在 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

以上例程在 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

参见


Math 函数
PHP Manual