(PHP 4, PHP 5, PHP 7, PHP 8)
bindec — Binary to decimal
Returns the decimal equivalent of the binary number represented by the binary_string argument.
bindec() converts a binary number to an int 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.
binary_string The binary string to convert. Any invalid characters in binary_string are silently ignored. As of PHP 7.4.0 supplying any invalid characters is deprecated.
The parameter must be a string. Using other data types will produce unexpected results.
The decimal value of binary_string
| Version | Description |
|---|---|
| 7.4.0 | Passing invalid characters will now generate a deprecation notice. The result will still be computed as if the invalid characters did not exist. |
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
$magnitude_lower = pow(2, (PHP_INT_SIZE * 8) - 2);
p($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
Note:
The function can convert numbers that are too large to fit into the platforms int type, larger values are returned as float in that case.