PHP preg_match - only allow alphanumeric strings and - _ characters

Question

I need the regex to check if a string only contains numbers, letters, hyphens or underscore

$string1 = \"This is a string*\";
$string2 = \"this_is-a-string\"         


        

Answer 1

if(!preg_match('/^[\w-]+$/', $string1)) {
   echo "String 1 not acceptable acceptable";
   // String2 acceptable
}