输入和正则表达式模式之间的PHP完全匹配

Question

I'm trying to build a check that reliably evaluates whether the input ($f_username) is a MAC Address via Regex 'cause there are different Syntax it could take. Upon finding a match. this should be transferred to lowercase without deliminators.

The function works fine in matching and transforming most input, but will wrongly match longer input... eg 11-22-33-44-55-66-77-88 would be transferred to 11-22-33-44-55-66 and $match is set to true...

This should cause the function to go to the "else branch" as is is not an exact match of the pattern... however it contains a match... does anybody have an idea how to properly match this ?

Thanks for taking the time to read this and thanks in advance for any answers :)

function username_check($f_username) {
  global $match;
  if (preg_match_all("/([0-9a-fA-F]{2})[^0-9a-fA-F]?([0-9a-fA-F]{2})[^0-9a-fA-F]?([0-9a-fA-F]{2})[^0-9a-fA-F]?([0-9a-fA-F]{2})[^0-9a-fA-F]?([0-9a-fA-F]{2})[^0-9a-fA-F]?([0-9a-fA-F]{2})/", $f_username, $output, PREG_PATTERN_ORDER)) {
    for ($i = 1; $i <= 6; $i++) {
      $new_username .= strtolower($output[$i][0]);
    }
    $match = true;
    $new_username = "'" . $new_username . "'"; //for later use in SQL-Query
  } else {
    $match = false;
  }
  return $new_username;
}

Answer 1

I recommend using the RegEx from this answer , as it ensures a well-formed MAC-address. If you want to add spaces to the list of delimiters, just replace this [-:] with this [: -] .

You are experiencing the problem you described because you haven't bound your RegEx to the start, or the end of a string. Which means that as long as there's a match somewhere inside the string it's a valid match.
To bind it to the start of a string, use ^ just after the opening delimiter. To bind it at the end of a string, I recommend* using \\z just before the closing delimiter.

* Reason I recommend \\z over $ , in PHP, is because the latter will allow a newline after the match. That means that the string "testing\\n" will match a pattern bound with $ , but not one bound with \\z . Most of the times you really do not want that newline.