How can I remove leading and trailing non-alphanumeric characters

Question

I\'m looking to \"trim\" non-alphanumerics from a string, similar to how trim() works with whitespace.

Help me convert #str|ng# to st

Answer 1

You don't need regex, use trim() and specify what to trim (it trims whitespace by default):

$string = trim($string, "#");

Docs: http://php.net/trim

Answer 2

Try using a ^\W+|\W+$ pattern like this:

$string = preg_replace('/^\W+|\W+$/', '', $string); 

This will replace any non-word characters (note this doesn't include underscores) which appear either at the beginning or end of the string. The | is an alternation, which will match any string which matches either the pattern on the left or the pattern on the right.

If you also need to remove underscores, use a character class like this:

$string = preg_replace('/^[\W_]+|[\W_]+$/', '', $string);