How to detect whether array key exists in php

Two methods: 1. Use "array_key_exists("specified key value", $arr)" and return true if it exists. 2. Use "isset($arr["specified key value"]" to check whether the value corresponding to the specified key name exists, and then determine whether the key exists. If it exists, it will return true.

The operating environment of this tutorial: Windows 7 system, PHP version 7.1, DELL G3 computer

Two methods for PHP to detect whether the array key exists:

1. Use array_key_exists() function

array_key_exists() function checks whether the specified key name exists in an array and returns true if the key name exists. , if the key name does not exist, return false.

<?php
header(&#39;content-type:text/html;charset=utf-8&#39;);   
$arr = array("Volvo" => "XC90", "BMW" => "X5");
if (array_key_exists("Volvo", $arr)) {
	echo "数组key存在!";
} else {
	echo "数组key不存在!";
}
?>

2. Use the isset() function

isset() function Used to detect whether the variable has been set and is not NULL.

Detection idea:

• Use array name["key"] to access the specified array element,

• Use isset() function to detect whether the array element exists

  If it exists and is not NULL, return TRUE, otherwise return FALSE.
  

<?php
header(&#39;content-type:text/html;charset=utf-8&#39;);   
$arr = array("Volvo" => "XC90", "BMW" => "X5");
if (isset($arr["a"])) {
	echo "数组key存在!";
} else {
	echo "数组key不存在!";
}
?>

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