PHP count() 函数

计算 car 节点的子节点个数：

   <?php
  $xml=<<<XML
   <cars>
   <car name="Volvo">
   <child/>
   <child/>
   <child/>
   <child/>
   </car>
   <car name="BMW">
   <child/>
   <child/>
   </car>
  </cars>
  XML;
  
  $elem=new SimpleXMLElement($xml);
  foreach ($elem as $car)
   {
   printf("%s has %d children.<br>", $car['name'], $car->count());
   }
  ?>