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?

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