PHP How to find a string in a string that does not occur next to a letter

A recent problem I've encountered

$string = 'Demetria Devonne';

if (strpos($string, 'Devon'))
{
    echo 'Devon';
}

Returns a result. But I need to only find matches for the specified word where a letter does not come before or after.

So running a check on words like

"Devons" or "Devonia"

would not result in a match.

But then something like

"From Devon, Uk"

would result in a match as there are no letters surrounding it.

Is there a function that can do this in PHP?

---

You will need to do this using regex, rather than string functions. Fortunately, this is very simple in this case.

if (preg_match('/\bDevon\b/', $string)) {
    echo 'Devon';
}

\b is a special character that means "word boundary", such as a comma or a space.