[php] PHP - regex to allow letters and numbers only

I have tried:

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

but im doing something wrong i guess.

You left off the / (pattern delimiter) and $ (match end string).

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

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

• Missing end anchor $
• Missing multiplier
• Missing end delimiter

So it should fail anyway, but if it may work, it matches against just one digit at the beginning of the string.

/^[a-z0-9]+$/i

try this way .eregi("[^A-Za-z0-9.]", $value)