How to detect whether array key exists in php

In PHP, you can use the array_key_exists() function to detect whether the specified array key exists. This function accepts two non-omitable parameters, the syntax is "array_key_exists(key,array)", if the key name exists Returns true, or false if the key name does not exist.

The operating environment of this tutorial: windows7 system, PHP7.1 version, DELL G3 computer

In PHP, you can use the array_key_exists() function To detect whether the specified array key exists.

array_key_exists() function checks whether the specified key exists in an array. If the key exists, it returns true. If the key does not exist, it returns false.

This function accepts two parameters that cannot be omitted:

array_key_exists(key,array)

Parameters	Description
key	Required. Specifies the key name.
array	Required. Specifies an array.

Example 1:

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

Please remember that if you omit the key name when specifying the array , will generate integer key names starting from 0 and increasing by 1.

Example 2: Check whether the integer key name "0" exists in the array

<?php
header(&#39;content-type:text/html;charset=utf-8&#39;);   
$a=array("Volvo","BMW");
if (array_key_exists(0,$a))
{
    echo "指定数组键存在";
}
else
{
    echo "指定数组键不存在";
}
?>

Recommended study: "PHP Video Tutorial 》

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