Communication Between RC4 Delphi <-> PHP

I'm just trying to translate this RC4 Function (PHP) to Delphi but i don't have any luck, it just corrupt data... Any help is appreciated.

This is the PHP Function:

function RC4($str, $key) {  
	$s = array();
	for ($i = 0; $i < 256; $i++) {
		$s[$i] = $i;
	}
	$j = 0;
	for ($i = 0; $i < 256; $i++) {
		$j = ($j + $s[$i] + ord($key[$i % strlen($key)])) % 256;
		$x = $s[$i];
		$s[$i] = $s[$j];
		$s[$j] = $x;
	}
	$i = 0;
	$j = 0;
	$res = '';
	for ($y = 0; $y < strlen($str); $y++) {
		$i = ($i + 1) % 256;
		$j = ($j + $s[$i]) % 256;
		$x = $s[$i];
		$s[$i] = $s[$j];
		$s[$j] = $x;
		$res .= $str[$y] ^ chr($s[($s[$i] + $s[$j]) % 256]);
	}
	return $res;
}

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And here is my try to translate to Delphi but it just corrupt data:

function RC4Delphi(str, key: string): string;
var
  s: array[0..255] of integer;
  i, j, x, y,f: integer;
  res: string;
begin
  for i := 0 to 255 do
    s[i] := i;
  j := 0;
  for i := 0 to 255 do
  begin
    j := (j + s[i] + ord(key[i mod length(key)])) mod 256;
    x := s[i];
    s[i] := s[j];
    s[j] := x;
  end;
  i := 0;
  j := 0;
  res := '';
  for y := 0 to length(str) do
  begin
    i := i mod 256;
    j := (j + s[i] mod 256);
    x := s[i];
    s[i] := s[j];
    s[j] := x;
    f:=  ord(str[y]) xor ord(chr(s[(s[i] + s[j]) mod 256]));

    res := res + chr(f);
  end;
  result := res;

end;

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