Regex in php - letters and numbers with limited length

Question

How do I make a regex that enforces:

• letters AND numbers (at least 1 of each)
• min and max length (10 to 50)
• nothing other than letters or numbers

when using a php preg_match?

---

Here's what I got:

 ^[A-Za-z0-9]{10,50}$

It seems to do everything except enforce letters AND numbers.

Answer 1

Do:

^(?=.*(?:[A-Za-z].*\d|\d.*[A-Za-z]))[A-Za-z0-9]{10,50}$

• (?=.*(?:[A-Za-z].*\d|\d.*[A-Za-z])) is zero width positive lookahead, this makes sure there is at least one letter, and one digit present

• [A-Za-z0-9]{10,50} makes sure the match only contains letters and digits

Demo

---

Or even cleaner, use two lookaheads instead of OR-ing (thanks to chris85):

^(?=.*[A-Za-z])(?=.*\d)[A-Za-z0-9]{10,50}$