Check for letters, numbers and spaces?

Question

I'm making a Full Name field and only want the user to be able to enter numbers, letters and spaces. How would that be done in an if statement?

Answer 1

You can go the opposite way and check if there are any illegal characters using, for instance:

if (preg_match("/[^a-z\\d ]/i", $input))
    // illegal input

Answer 2

Another solution,

if(preg_match('/[^\w\d ]/',$input)){
    //illegal input
}