[SOLVED] PHP convert hex to float

PHP convert hex to float

Hi I am trying to convert the hex value into float the method I am using is

function hex2float($strHex) {
$hex = sscanf($strHex, "%02x%02x%02x%02x%02x%02x%02x%02x");
$hex = array_reverse($hex);
$bin = implode('', array_map('chr', $hex));
$array = unpack("dnum", $bin);
return $array['num'];
}

$float = hex2float('4019999a');
echo $float;

Output

The output it's returning is 6.4000015258789 but in actual it should be 2.4

See reference

Solution

Your problem is that you are interpreting the value in little endian byte order. This gives you the incorrect value of 6.4, which is actually -6.3320110435437E-23. Additionally, you are unpacking this as a double-precision float. It's not. It's single precision (only 4 bytes wide).

function hex2float($strHex) {
    $hex = sscanf($strHex, "%02x%02x%02x%02x%02x%02x%02x%02x");
    $bin = implode('', array_map('chr', $hex));
    $array = unpack("Gnum", $bin);
    return $array['num'];
}

$float = hex2float('4019999a');
echo $float;

This gives you the correct value of 2.4.

An easier way to do this is var_dump(unpack('G', hex2bin('4019999a'))[1]); which also gives you the correct value.