For any char with ord($char) < 16 you get a HEX back which is only 1 long. You forgot to add 0 padding.
This should solve it:
<?php
function strToHex($string){
$hex = '';
for ($i=0; $i<strlen($string); $i++){
$ord = ord($string[$i]);
$hexCode = dechex($ord);
$hex .= substr('0'.$hexCode, -2);
}
return strToUpper($hex);
}
function hexToStr($hex){
$string='';
for ($i=0; $i < strlen($hex)-1; $i+=2){
$string .= chr(hexdec($hex[$i].$hex[$i+1]));
}
return $string;
}
// Tests
header('Content-Type: text/plain');
function test($expected, $actual, $success) {
if($expected !== $actual) {
echo "Expected: '$expected'\n";
echo "Actual: '$actual'\n";
echo "\n";
$success = false;
}
return $success;
}
$success = true;
$success = test('00', strToHex(hexToStr('00')), $success);
$success = test('FF', strToHex(hexToStr('FF')), $success);
$success = test('000102FF', strToHex(hexToStr('000102FF')), $success);
$success = test('???§P?§P ?§T?§?', hexToStr(strToHex('???§P?§P ?§T?§?')), $success);
echo $success ? "Success" : "\nFailed";