PHP allows you to associate name/label with each array of elements in PHP using => symbol. In such a way, you can easily remember the element because each element is represented by label than an incremented number.

Definition : 
There is two Method to define an associative array:

First Method :

$ages=array("Kapil"=>"25","Lakhan"=>"36","Sonia"=>"18");  

Second Method :

$ages["Kapil"]="25";  
$ages["Lakhan"]="36";  
$ages["Sonia"]="18";  

Example

File Name :first_associativearray.php

<?php    
$ages=array("Kapil"=>"25","Lakhan"=>"36","Sonia"=>"18");  
echo "Kapil Age: ".$ages["Kapil"]."<br/>";  
echo "Lakhan Age: ".$ages["Lakhan"]."<br/>";  
echo "Sonia Age: ".$ages["Sonia"]."<br/>";  
?>    

Output:

Kapil Age: 25  
Lakhan Age: 36  
Sonia Age: 18  

File Name: second_associativearray.php

<?php     
$ages["Kapil"]="25";  
$ages["Lakhan"]="36";  
$ages["Sonia"]="18";  
echo "Kapil Age: ".$ages["Kapil"]."<br/>";  
echo "Lakhan Age: ".$ages["Lakhan"]."<br/>";  
echo "Sonia Age: ".$ages["Sonia"]."<br/>";  
?> 

Output:

Kapil Age: 25  
Lakhan Age: 36  
Sonia Age: 18 

 Traversing PHP Associative Array / Using Loops with Associative Arrays

• With the help of PHP for each loop, we can easily traverse the elements of PHP associative array.
• Because the indices in this associative array are not numbers, we cannot use a simple counter in a for loop to work with the array. We can use the foreach loop or the list() and each() constructs.
• The foreach loop has a slightly different structure when using associative arrays. We can use it exactly as we did in the previous example, or we can incorporate the keys as well:

<?php    
$ages=array("Kapil"=>"25","Lakhan"=>"36","Sonia"=>"18");
foreach($ages as $key => $ag) {  
echo "Key: ".$key." Value: ".$ag."<br/>";  
}      
?>

Output:

Key: Kapil Age: 25  
Key: Lakhan Age: 36  
Key: Sonia Age: 18