PHP 函数 ctype_lower()

<?php
   $strings = array('aac123', 'testing', "testin IS Done");

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