The difference between isset and array_key_exists in PHP functions_PHP tutorial

When determining whether the index value of a certain PHP array exists, two methods, <font face="NSimsun">isset</font> and <font face="NSimsun">array_key_exists</font>, are generally used.

isset($a['key'])
array_key_exists('key', $a)

<font face="NSimsun">array_key_exists</font> tells you exactly whether a certain key exists in the array, while <font face="NSimsun">isset</font> just returns the status of whether the key value is <font face="NSimsun">null</font>. That is, assuming the following array is given:

$a = array('key1' => '123', 'key2' => null);

Use these two methods to determine the existence of key values. The results are as follows:

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

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

From the perspective of the PHP engine itself, the bottom layer is implemented in C language. Both <font face="NSimsun">array_key_exists</font> and <font face="NSimsun">isset</font> should be very fast. If the number of operations is thousands or tens of thousands, the performance of <font face="NSimsun">isset</font> should be more significant in this case.

http://www.bkjia.com/PHPjc/363774.htmlwww.bkjia.comtruehttp: //www.bkjia.com/PHPjc/363774.htmlTechArticleTo determine whether the index value of a PHP array exists, isset and array_key_exists are generally used. isset($a['key'])array_key_exists('key', $a) array_key_exists exactly...