PHP中的count对数组以及字符串统计

1：空值

<?php
   $str = "";
   echo count($str);
>

2：字符串

<?php
   $str = "advddsdfff";
   echo count($str);
?>

3:空数组

<pre name="code" class="php"><pre name="code" class="php"><?php
   $str = array();
   echo count($str);
?>

输出 0；

4：正常数组

<?php
   $str = array("a","b","c");
   echo count($str);
?>