The difference between php isset and array_key_exists to check whether a certain value exists in the array

Original address: http://ivhong.com/?p=110 (ivhong.com is the main address of my blog)

First take a look at the following code. What do you think the result is?

//定义一个数组, > 5.4
$arr = ['a' => null];
var_dump(isset($arr), array_key_exists('a', $arr));

---------------------Here are the results---------------------- -------

/*
 * 输出
 *bool(false)
 *bool(true)
 */

//isset 的用法是： 检测变量是否设置，并且不是 NULL。所以会有上面的输出
//如果判断数组中是否存在某个键值，还是乖乖的用 array_key_exists 吧，不然就是给自己挖了一个巨隐藏的坑啊！！！

The above introduces the difference between php isset and array_key_exists to check whether a certain value exists in the array, including the content. I hope it will be helpful to friends who are interested in PHP tutorials.