How to remove all non alphanumeric characters from a string with Regular Expressions
If you have a string that can only contains alphanumeric values, it is a lot simpler to state the type of characters that are allowed, instead of looking up every possible symbol on the planet and banning it.
Here then is a regular expression that will remove every none-alphanumeric character. The [^ indicates that this is a negative regular expression, the a-zA-Z0-9 allows any kind of regular expression, the \s represents whitespaces, and there you go basically. Use this correctly and you are well on your way to removing all unwanted characters!
$string = "Let's %&/( do some $ string cleaning: @o@#k?? -_";
$string = preg_replace('/[^a-zA-Z0-9\s]+/', '', $string);
Lets do some string cleaning ok