PHP - regex to allow letters and numbers only

Question

I have tried:

preg_match(\"/^[a-zA-Z0-9]\", $value)

but im doing something wrong i guess.

Answer 1

As the OP said that he wants letters and numbers ONLY (no underscore!), one more way to have this in php regex is to use posix expressions:

/^[[:alnum:]]+$/

Note: This will not work in Java, JavaScript, Python, Ruby, .NET