Encoding/decoding string in hexadecimal and back

Question

Given a string that may contain any character (including a unicode characters), how can I convert this string into hexadecimal representation, and then reverse and obtain from hexadecimal this string?

Solution 1

Use pack() and unpack():

function hex2str( $hex ) {
  return pack('H*', $hex);
}

function str2hex( $str ) {
  return array_shift( unpack('H*', $str) );
}

$txt = 'This is test';
$hex = str2hex( $txt );
$str = hex2str( $hex );

echo "{$txt} => {$hex} => {$str}\n";

would produce

This is test => 546869732069732074657374 => This is test

Solution 2

Use a function like this:

<?php
function bin2hex($str) {
    $hex = "";
    $i = 0;
    do {
        $hex .= dechex(ord($str{$i}));
        $i++;
    } while ($i < strlen($str));
    return $hex;
}

// Look what happens when ord($str{$i}) is 0...15
// you get a single digit hexadecimal value 0...F

// bin2hex($str) could return something like 4a3,
// decimals(74, 3), whatever the binary value is of those.

function hex2bin($str) {
    $bin = "";
    $i = 0;
    do {
        $bin .= chr(hexdec($str{$i}.$str{($i + 1)}));
        $i += 2;
    } while ($i < strlen($str));
    return $bin;
}

// hex2bin("4a3") just broke. Now what?

// Using sprintf() to get it right.
function bin2hex($str) {
    $hex = "";
    $i = 0;
    do {
        $hex .= sprintf("%02x", ord($str{$i}));
        $i++;
    } while ($i < strlen($str));
    return $hex;
}

// now using whatever the binary value of decimals(74, 3)
// and this bin2hex() you get a hexadecimal value you can
// then run the hex2bin function on. 4a03 instead of 4a3.
?>

Source: http://php.net/manual/en/function.bin2hex.php