PHP function array_key_exists() that checks whether the specified key exists in the array

Example

Check whether the key name "Volvo" exists in the array:

<?php
$a=array("Volvo"=>"XC90","BMW"=>"X5");
if (array_key_exists("Volvo",$a))
{
echo "Key exists!";
}
else
{
echo "Key does not exist!";
}
?>

Definition and usage

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

Tip: Please remember that if you omit the key name when specifying the array, an integerkey name starting from 0 and increasing by 1 will be generated. (See Example 2)

Syntax

array_key_exists(key,array)

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

Technical details

Return value:	Returns TRUE if the key name exists, if If the key name does not exist, FALSE is returned.
PHP version:	4.0.7+

More examples

Examples 1

Check whether the key name "Toyota" exists in the array:

<?php
$a=array("Volvo"=>"XC90","BMW"=>"X5");
if (key_exists("Toyota",$a))
{
echo "Key exists!";
}
else
{
echo "Key does not exist!";
}
?>

Example 2

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

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

Example 1

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

Output:

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!"; 
} 
?>

Output:

Key does not exist!

Example 2

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

Output:

Key exists!

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