base_convert
ceil
Math Functions
PHP Manual

# bindec

(PHP 4, PHP 5)

bindec — Binary to decimal

### Description

number bindec ( string `$binary_string` )

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.

### Parameters

`binary_string`

  The binary string to convert

Warning

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

### Return Values

The decimal value of `binary_string`

### Changelog

Version | Description
--- | ---
Since 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.

### 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

### See Also

- decbin() - Decimal to binary
- octdec() - Octal to decimal
- hexdec() - Hexadecimal to decimal
- base_convert() - Convert a number between arbitrary bases

base_convert
ceil
Math Functions
PHP Manual