PHP array_key_exists() Function

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# PHP array_key_exists() Function

Complete PHP Array Reference

## 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

From http://www.w3schools.com (Copyright Refsnes Data)