Question

I don’t want preg_match_all … because the form field only allows for numbers and letters… just wondering what the right syntax is…

Nothing fancy … just need to know the right syntax for a preg_match statement that looks for only numbers and letters. Something like

preg_match('/^([^.]+)\.([^.]+)\.com$/', $unit)

But that doesn’t look for numbers too….

Answer 1

If you just want to ensure a string contains only alphanumeric characters. A-Z, a-z, 0-9 you don’t need to use regular expressions.

Use ctype_alnum()

Example from the documentation:

<?php
$strings = array('AbCd1zyZ9', 'foo!#$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";
    }
}
?>

The above example will output:

The string AbCd1zyZ9 consists of all letters or digits.
The string foo!#$bar does not consist of all letters or digits.