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php-如何检查一个变量是否被设置,并且值为NULL

WBOY
WBOYOriginal
2016-06-02 11:32:00902browse

php编程语言

最近有一个小问题,就是如何在php中检查一个变量是否被设置并且值为null,看看大家都有什么好的解决方案?谢谢~~

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