email validation

Hi, i was wondering if some1 could tell me the code to validate an email for incorrect charactors.
I believe it is something like this but i am not to sure

PHP Code:

---

  if (ereg('^[a-zA-Z0-9_\.\-]+@[a-zA-Z0-9\-]+\.[a-zA-Z0-9\-\.]+$', $address))
    return true;
  else 
    return false;
} 


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also how can i check for certain fields to be field in. i.e my form has 4 text fields ($name,$message,$email,$contact number)

i want name,message and email to be filled in but contact number is optional. i cant figure out how to exclude contact number

Thanks Adam

Your e-mail validation expression looks a little strict. The first part of the e-mail address before the @ sign can contain an number of other special characters. Users can enter the email address "[email protected]", which is clearly invalid but not "d^[email protected]", which is valid. You may want to look into more advanced checking of the e-mail address.

This article describes some of them: http://coveryourasp.com/ValidateEmail.asp#Result1

This gives a regular expression e-mail syntax checker. You can see just how many characters are valid in an e-mail address.

http://www-2.cs.cmu.edu/~cache/email/

Checking for optional fields is easy. You just need to check for an empty string in variable. For example the following checks if the field "contact" had anything entered:

PHP Code:

---

if ($_REQUEST['contact'] == '') 
  /* nothing entered */
else
  /* something was entered */ 


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