regex - Identical Strings in PHP not matching

I'm trying to compare two strings (one from my database and another supplied by the user) and see if they match! The problem I'm having is that they don't seem to match - even though the strings seems to be exactly identical?

My PHP code is below:

public function Verify($pdo, $id, $token) {

    $prepsql = $pdo->prepare("SELECT * FROM Profiles WHERE id = '$id' LIMIT 1");
    $prepsql->execute();
    $currentrow = $prepsql->fetch();
    $current = preg_replace("/[^a-zA-Z0-9]+/", "", $currentrow["token"]);
    echo '
'.var_dump($current).'
';
    echo '
'.var_dump($token).'
';
    $token = preg_replace("/[^a-zA-Z0-9]+/", "", $token);
    if ($current == null || $current = "") {
        return false;
    } else {

        if (strcmp($token, $current) == 0) {
            return true;
        } else {
            return false;
        }
    }
}

And here is the webpage output:

  string(244) "CAAW4HRuZBuB4BACA7GffOAwLHgmLgMMLGQxDAw8IJDCwahZAh0S4wZAcP8Q9DmMwsDpBq7jFcH1EzUIsZBbhKov12utoYFQns0HhgB5xKLeDqtZBRqavaNjNSn7KAcObZAEcavQCRbGlVKZBArfDEHskBSR8qAoU543DVTZCOyHm5oYNDVafwHl0bAkc4jyIhh2YHEPaNpWGC0FhezsSidOgLjnfFq8CeLVxHH0nUZBMLgAZDZD"
string(244) "CAAW4HRuZBuB4BACA7GffOAwLHgmLgMMLGQxDAw8IJDCwahZAh0S4wZAcP8Q9DmMwsDpBq7jFcH1EzUIsZBbhKov12utoYFQns0HhgB5xKLeDqtZBRqavaNjNSn7KAcObZAEcavQCRbGlVKZBArfDEHskBSR8qAoU543DVTZCOyHm5oYNDVafwHl0bAkc4jyIhh2YHEPaNpWGC0FhezsSidOgLjnfFq8CeLVxHH0nUZBMLgAZDZD"
Not authenticated

Not authenticated just means that this function is returning false...

What on earth am I doing wrong? As per advice given on other similar answers, I've used the regex function to basically only keep alphanumeric characters but that has made no difference? It isn't a trimming issue either as that didn't work!

Any help would be much appreciated!

Thanks!

Answer

Here is your problem:

if ($current == null || $current = "") {
//                               ^ now `$current` is "", an empty string

You assign a new value to $current, an empty string.

You probably want something like:

if ($current == null || $current == "") {
//                               ^^ now you are comparing