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Rechercher une fonction PHP

bindec

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(PHP 4, PHP 5, PHP 7)

bindec — Binary to decimal

Description

bindec ( string $binary_string ) : number

Returns the decimal equivalent of the binary number represented by the binary_string argument.

bindec() converts a binary number to an integer or, if needed for size reasons, float.

bindec() interprets all binary_string values as unsigned integers. This is because bindec() sees the most significant bit as another order of magnitude rather than as the sign bit.

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Parameters

binary_string

The binary string to convert

Warning

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

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Return Values

The decimal value of binary_string

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Examples

Example #1 bindec() example

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

echo bindec('111');
?>

The above example will output:

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";
}
?>

Output of the above example on 32 bit machines:

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

Output of the above example on 64 bit machines:

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

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Notes

Note:

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

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See Also

Find a PHP function

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Document created the 30/01/2003, last modified the 26/10/2018
Source of the printed document:https://www.gaudry.be/en/php-rf-function.bindec.html

The infobrol is a personal site whose content is my sole responsibility. The text is available under CreativeCommons license (BY-NC-SA). More info on the terms of use and the author.

References

  1. View the html document Language of the document:fr Manuel PHP : http://php.net

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