What the struct "zend_ptr_stack" means in Zend of PHP?
<p>At line 29 of "Zend/zend_globals.h" in PHP-5.2.17.</p>

<p>What the struct "zend_ptr_stack" means and what's the use of this struct?</p>

<pre><code>typedef struct _zend_ptr_stack {
    int top, max;
    void **elements;
    void **top_element;
} zend_ptr_stack;
</code></pre>
