$zz = '/this\b/';

$string1 = "this is a apple";

$string2 = "thisis a apple";

$string3 = "thisartrapple";

if (preg_match($zz, $string3, $matches)) {

echo '匹配到了，结果为：';

var_dump($matches);

} else {

echo '没有匹配到';

}

?>