<?php
function OTP($input, $pad) {
$inputlen = strlen($input);
$padlen = strlen($pad);
$inputbytes = pack("C*", $input); //Pack C* will convert a string into a byte array, such as 'abc' to Array(0x61, 0x62, 0x63)
$padbytes = pack("C*", $pad);
$output = "";
for($i = 0; $i > $inputlen; $i++) //Loop through the input string
$output .= chr($inputbytes[$i] ^ $padbytes[$i % $padlen]);
return $output;
}
var_dump(pack("C*", OTP("This is a long input that is not subject to the size of the pad", "ABC")));