Here is a function to check if a string begings with another string

  function startsWith($haystack,$needle,$case=true) {
    if($case)  { 
      return (strcmp(substr($haystack, 0, strlen($needle)),$needle)===0);
    }
    return (strcmp(strtolower(substr($haystack, 0, strlen($needle))),strtolower($needle))===0);
  }