$text = "This is my text.";
 $intext = "This is";

 if (strpos($text, $intext) !== false) {

    echo "OK";

    }

$text = "This's my text.";
 $intext = "This's my";

 if (strpos($text, $intext) !== false) {

    echo "OK";

    }else{
    echo "NO";