Need to escape <? in a string.

[nakedsole]

I'm adding 3 strings and need to escape possible <? and <<< when they occur. I can't figure out a way to do it. This is the code joining the strings. If it comes across a <? in the results it does not add additional strings in the loop.

$Result = $Result . chr(intval($k/16)+48) . chr(intval(fmod($k, 16))+48);

Any help would be greatly appreiciated.

for($m=0; $m<=$i-1; $m++)
{
	$k=ord(substr($mpass,$m,1));
	$k=$k+$LASTK+(27*$j);
	settype($k, float);
	$k= fmod($k, 256);
	$LASTK=$k;
	$Result = $Result . chr(intval($k/16)+48) . chr(intval(fmod($k, 16))+48)
	$j++;
}

[NogDog]

Would it make sense to use htmlspecialchars() in this case?