Verifying If a Key Exists in an Array in PHP

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Q

How Do You Know If a Key Is Defined in an Array in PHP?

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A

There are two functions can be used to test if a key is defined in an array or not:

array_key_exists($key, $array) - Returns true if the $key is defined in $array.
isset($array[$key]) - Returns true if the $key is defined in $array.

Here is a PHP example script:

<?php 
$array = array("Zero"=>"PHP", "One"=>"Perl", "Two"=>"Java");
print("Is 'One' defined? ".array_key_exists("One", $array)."\n");
print("Is '1' defined? ".array_key_exists("1", $array)."\n");
print("Is 'Two' defined? ".isset($array["Two"])."\n");
print("Is '2' defined? ".isset($array[2])."\n");
?>

This script will print:

Is 'One' defined? 1
Is '1' defined?
Is 'Two' defined? 1
Is '2' defined?

⇒ Finding a Given Value in an Array in PHP

⇐ Counting the Number of Values in an Array in PHP

⇑ PHP Built-in Functions for Arrays

⇑⇑ PHP Tutorials

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