Question

Unfortunately, for some strange reason the regex method isn’t working for me with UTF-8 (preg_replace + UTF-8 doesn't work on one server but works on another).

What would be the most efficient way to accomplish my goal without using regex?

Just to make it as clear as possible, for the following set of words:
cat, dog, sky

cats would return false
the sky is blue would return true
skyrim would return false

Answer 1

Super short example but it’s the way I’d do it without Regex.

$haystack = "cats"; //"the sky is blue"; // "skyrim";
$needles = array("cat", "dog", "sky");

$found = false;
foreach($needles as $needle)
    if(strpos(" $haystack ", " $needle ") !== false) {
        $found = true;
        break;
    }


echo $found ? "A needle was found." : "A needle was not found.";