preg_match()

Does input string match regex expression

  $InputString = "abcd";
  $Length = strlen($InputString);
  $RegexPattern = '^[(]*([0-9]{3})[- .)]*[0-9]{3}[- .]*[0-9]{4}$';
  if (
      ($Length > 2) && ($Length < 100) &&    //Testing for length first protects against malicious very long inputs
      (preg_match($RegexPattern, InputString))   //Returns 1 if regex matches
  {

 

  } 

preg_replace()

Replace any characters that don’t match the regex expression with character from another string.

You can make the replacement string empty to simply remove unwanted characters

Remove all characters that are not numbers example

  $InputString = "01-23(4)";
  $RegexPattern = "[^0-9]";
  $FormattedNumber = preg_replace($RegexPattern, "", $InputString)
  //$FormattedNumber = "01234"