Check if string has only numbers and letters

Checks if all of the characters in the provided string, text, are alphanumeric.

$strings = array('AbCd1zyZ9', 'foo!#$bar');
foreach ($strings as $testcase) {
    if (ctype_alnum($testcase)) {
        echo "The string $testcase consists of all letters or digits.n";
    } else {
        echo "The string $testcase does not consist of all letters or digits.n";
    }
}