PHP 函数 ctype_cntrl()

<?php
   $strings = array('\n\r\t', 'example1234r');

   foreach ($strings as $test) {
      if (ctype_cntrl($test)) {
         echo "$test consists of all control characters. \n";
      }else {
         echo "$test does not have all all control characters. \n";
      }
   }
?>