Encoding/decoding string in hexadecimal and back - php

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?

Answer 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

Answer 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