class_exists() function

The class_exists() function is used to determine whether or not a class is defined in the script. It returns a boolean value of either TRUE or FALSE.

example.php

<?php
/* 
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website: http://4evertutorials.blogspot.in/
*/

include_once("cart.php");
if(class_exists("cart")){
    $shopping_cart = new cart();
    echo $shopping_cart->store;
} else {
    echo '"cart" class does not exist';
}


?>

cart.php

<?php
/* 
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website: http://4evertutorials.blogspot.in/
*/


class cart {

    public $store = "Spacely Sprockets";
    public $items = array();
}

?>