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PHP array_key_exists() Function

Definition and Usage

The array_key_exists() function checks an array for a specified key, and returns true if the key exists and false is the key does not exist.

Syntax

array_key_exists(key,array)

Parameter	Description
key	Required. Specifies the key
array	Required. Specifies an array

Tips and Notes

Tip: Remember that if you skip the key when you specify an array, an integer key is generated, starting at 0 and increases by 1 for each value. (See example 3)

Example 1

<?php
$a=array("a"=>"Dog","b"=>"Cat");
if (array_key_exists("a",$a))
	{
	echo "Key exists!";
	}
else
	{
	echo "Key does not exist!";
	}
?>

The output of the code above will be:

Key exists!

Example 2

<?php
$a=array("a"=>"Dog","b"=>"Cat");
if (array_key_exists("c",$a))
	{
	echo "Key exists!";
	}
else
	{
	echo "Key does not exist!";
	}
?>

The output of the code above will be:

Key does not exist!

Example 3

<?php
$a=array("Dog",Cat");
if (array_key_exists(0,$a))
	{
	echo "Key exists!";
	}
else
	{
	echo "Key does not exist!";
	}
?>

The output of the code above will be:

Key exists!

Complete PHP Array Reference