Question

I want to use a basic regular expression to check whether a string contains only numbers and alphabet characters so I tried

preg_match('[a-zA-Z0-9]*', $address)

Which unfortunately returns an error:

Warning: preg_match() [function.preg-match]: Unknown modifier ‘*’ in /bla/bla.php on line XX

It’s a simple regex. Where am I getting it wrong?

Answer 1

The pattern should begin and end with a pattern delimiter. Different preg options, like case-insensitive search can be added after the delimiter. Usually slash (/) is used for delimiter, but can be any symbol (the delimiter should be escaped in the pattern):

preg_match('/[a-z0-9]*/i', $address);

This will check if the string has numbers or characters in it.

If you want to make sure that it has only numbers and characters, then use this:

preg_match('/^[a-z0-9]*$/i', $address);