Validating Characters

[Kryptix]

I need to validate form submission to check every character they have entered is a-z, A-Z, 0-9 and either a underscore or a space. How would I do this? Add every character to an array and then check or is there a better way?

[cags]

This topic is marked as 'Solved' so I assume the OP worked it out but in case anybody else reads this, there are lots of ways, here's one..

 

if(preg_match('#[^a-z0-9_ ]+#i', $input)) {
   // invalid characters
} else {
   // no invalid characters
}