Need help with a complex regular expression – how to ONLY allow characters and number

I’ve got is a system where users can duplicate directories

I want the user to be only allowed to enter characters and numbers when choosing a new name for the duplicated directory

ALL other characters should be left out AND white space characters need to be replaced with a single ‘-‘ (no matter how many of them)

I’ve got this to replace white space characters:

$str = preg_replace(‘%s+%’,’-‘, $str);

But I’m a little clueless as to how to replace ANY other character that isn’t a character or number

ANY help would be appreciated

Thanks

OM

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