Differences between PHP functions isset and array_key_exists

This article introduces the differences in usage of PHP's two functions isset and array_key_exists. Friends in need can refer to them. PHP determines whether the index value of an array exists. Generally, isset and array_key_exists are used. For example:

<?php isset($a['key'])
array_key_exists('key', $a)

The array_key_exists function will tell you exactly whether a key exists in the array, while isset just returns the status of whether the key value is null. Suppose you are given the following array: $a = array('key1' => '123', 'key2' => null); Use these two methods to determine the existence of key values. The results are as follows:

<?php isset($a['key1']);             // true
array_key_exists('key1', $a);  // true

isset($a['key2']);             // false
array_key_exists('key2', $a);  // true

Regarding the execution efficiency of these two functions: From the perspective of the PHP engine itself, the bottom layer is implemented in C language, and array_key_exists and isset should be very fast. If the number of operations is thousands or tens of thousands, the performance of isset should be more significant in this case.