BINDEC(3) 1 BINDEC(3)
bindec - Binary to decimal
SYNOPSIS
number bindec (string $binary_string)
DESCRIPTION
Returns the decimal equivalent of the binary number represented by the $binary_string argument.
bindec(3) converts a binary number to an integer or, if needed for size reasons, float.
bindec(3) interprets all $binary_string values as unsigned integers. This is because bindec(3) sees the most significant bit as another
order of magnitude rather than as the sign bit.
PARAMETERS
o $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
EXAMPLES
Example #1
bindec(3) example
<?php
echo bindec('110011') . "
";
echo bindec('000110011') . "
";
echo bindec('111');
?>
The above example will output:
51
51
7
Example #2
bindec(3) 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
";
$format = '%0' . (PHP_INT_SIZE * 8) . 'b';
$bin = sprintf($format, $input);
echo "binary: $bin
";
ini_set('precision', 20); // For readability on 64 bit boxes.
$dec = bindec($bin);
echo 'bindec(): ' . $dec . "
";
if ($note) {
echo "NOTE: $note
";
}
echo "
";
}
?>
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
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.
SEE ALSO
decbin(3), octdec(3), hexdec(3), base_convert(3).
PHP Documentation Group BINDEC(3)