preg_match: number-alphabets and commas only

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

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.