PHP preg_match for only numbers and letters, no special characters

If you want to match more than 1, then you'll need to, however, provide us with some code and we can help better.

although, in the meantime:

preg_match("/([a-zA-Z0-9])/", $formContent, $result);
print_r($result);

:)

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.

if(preg_match("/[A-Za-z0-9]+/", $content) == TRUE){

} else {

}