Question

How do I write a regular expression which matches number-alphabets and commas only?

I came out with this one below but it doesnt work – it accepts other punctuation marks as well!

# check for matches number-alphabets and commas only
  if(!preg_match('/([a-zA-Z0-9]|[a-zA-Z0-9\,])/', $cst_value))
  {
   $error = true;
   echo '<error elementid="usr_username" message="'.$cst_name.' - please use number-alphabets and commas only."/>';
  }

Many thanks,
Lau

Answer 1

You want:

/^[a-zA-Z0-9,]+$/

You need the start ^ and end $ of string anchors. Without them the regex engine will look for any of those characters in the string and if it finds one, it will call it a day and say there’s a match. With the anchors, it forces the engine to look at the whole string. Basically:

• /[a-zA-Z0-9,]+/ matches if any of the characters are alphanumeric + comma.
• /^[a-zA-Z0-9,]+$/ matches if all of the characters are alphanumeric + comma.