regex to match letters, numbers, certain symbols

Question

I need to validate a username in php, it can be:

• Letters (upper and lower case)
• Numbers
• Any of these symbols :.,?!@
• up to 15 characters OR 16 if the last character is one of the following #$^ (it can also be 15 or less with one of these 3 characters at the end only)

How do I do this?

Answer 1

Start with this:

/^[a-zA-Z0-9:.,?!@]{3,15}[#$^]?$/

then refine it to your needs. Try to see if you need escaping of the special char, but you should get the idea.

This means: from a to z, from A to Z, from 0 to 9 and :.,?!@ repeated from 3 to 15 times, optionally followed by one among #$^