php的一个函数运用注意
php的一个函数使用注意
???????? php中有一个函数extract()，不少人都使用过，但是这个函数时间上存在一个小小的隐患，如果使用不当可能会造成安全上的问题。
对于数组中的每个元素，键名用于变量名，键值用于变量值。
第二个参数 type 用于指定当某个变量已经存在，而数组中又有同名元素时，extract() 函数如何对待这样的冲突。
本函数返回成功设置的变量数目。
?一般第二个参数我们都会懒得设置，这样实际上存在一个变量覆盖的问题，由于这个函数的隐蔽性，很多时候我们会忽略掉它的危害性，结果就会造成黑客通过对数组元素的控制，或者说伪造，直接可以覆盖掉已经存在的某些变量，可以导致多种问题，包括本地包含漏洞，sql注入漏洞（通过这个函数很容易绕过变量检查），而且由于它的隐蔽性，很多人会忽略掉。明显的一个例子
???
?就是phpcms中的这个问题，而且通过对phpcms v9代码的查阅，里面错误使用extract的地方还有很多。这是值得程序员注意的一个问题。?
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