Email validation with PHP

How many times did you lose something or someone's contact info because your script fails to do a basic email validation and simply sends out emails? There are a lot of reasons why you should copy this function and use it right away to validate your user's input (spammers, bots, some persons write so bad that there's no wonder that the email is not valid etc.)... You need to do a validation and tell them if something was wrong so they can correct that error right away. You need a function to check that email address that they type.

The following PHP function is the best I've found over the internet, I'm sure there are lots of them out there to do an email validation but this one seems complete to me:

function check_email($email) {
  // First, we check that there's one @ symbol, and that the lengths are right
  if (!ereg("^[^@]{1,64}@[^@]{1,255}$", $email)) {
    // Email invalid because wrong number of characters in one 
//section, or wrong number of @ symbols.
    return false;
  }
  // Split it into sections to make life easier
  $email_array = explode("@", $email);
  $local_array = explode(".", $email_array[0]);
  for ($i = 0; $i < sizeof($local_array); $i++) {
     if (!ereg("^(([A-Za-z0-9!#$%&#038;'*+/=?^_`{|}~-]
[A-Za-z0-9!#$%&#038;'*+/=?^_`{|}~\.-]{0,63})|(\"[^(\\|\")]{0,62}\"))$", 
$local_array[$i])) {
      return false;
    }
  }  
  if (!ereg("^\[?[0-9\.]+\]?$", $email_array[1])) { // Check if domain is IP. 
//If not, it should be valid domain name
    $domain_array = explode(".", $email_array[1]);
    if (sizeof($domain_array) < 2) {
        return false; // Not enough parts to domain
    }
    for ($i = 0; $i < sizeof($domain_array); $i++) {
      if (!ereg("^(([A-Za-z0-9][A-Za-z0-9-]{0,61}
[A-Za-z0-9])|([A-Za-z0-9]+))$", $domain_array[$i])) {
        return false;
      }
    }
  }
  return true;
} 

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