2.5 变量的检索

首先我们定义了一个指向指针的指针，然后通过zend_hash_find去EG(active_symbol_table)作用域下寻找名称为foo($foo)的变量，如果成功找到，此函数将返回SUCCESS。看完代码，你肯定有很多疑问。为什么还要进行运算，fooval明明是zval**型的，为什么转成void**的？而且为什么还要进行&fooval运算，fooval本身不就已经是指向指针的指针了吗？:-)，该回答的问题确实很多，不要过于担心，让我们带着这些问题继续往下走。

所以当我们去HashTable里寻找变量的时候，得到的值其实是一个zval的指针。In order to populate that pointer into a calling function’s local storage,the calling function will naturally dereference the local pointer,resulting in a variable of indeterminate type with two levels of indirection (such as void**).Knowing that your “indeterminate type” in this case is zval*,you can see where the type being passed into zend_hash_find() will look different to the compiler,having three levels of indirection rather than two.This is done on purpose here so a simple typecast is added to the function call to silence compiler warnings.

就去符号表里找变量而言，SUCCESS和FAILURE仅代表这个变量是否存在而已。