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如题,之前判断是否存在不是用isset吗? 现在用exists 。。。 这俩有什么区别呢?
What is the difference between isset and exists? -PHP Chinese website Q&A-What is the difference between isset and exists? -PHP Chinese website Q&A
Please watch and learn.
1.对于数组值的判断不同,对于值为null或''或false,isset返回false,array_key_exists返回true;
2. 执行效率不同,isset是内建运算符,array_key_exists是php内置函数,isset要快一些。请参考:PHP 函数实现原理及性能分析
3.当用isset访问一个不存在索引数组值时,不会引起一个E_NOTICE的php错误消息;
4.array_key_exists 会调用get_defined_vars判断数组变量是否存在,isset不用;
What is the difference between isset and exists? -PHP Chinese website Q&A-What is the difference between isset and exists? -PHP Chinese website Q&A
Please watch and learn.
1.对于数组值的判断不同,对于值为null或''或false,isset返回false,array_key_exists返回true;
2. 执行效率不同,isset是内建运算符,array_key_exists是php内置函数,isset要快一些。请参考:PHP 函数实现原理及性能分析
3.当用isset访问一个不存在索引数组值时,不会引起一个E_NOTICE的php错误消息;
4.array_key_exists 会调用get_defined_vars判断数组变量是否存在,isset不用;