Iterating through object variables

Deep down in the heart of PHP, an object isn't really all that different from an array - an object has pointers to the functions of its class, sure, but otherwise it just stores variables. As a result, we can treat an object as an array with the foreach loop, and it will iterate through each of the variables inside that object - as long as they are accessible. That is, private and protected variables will not be accessible in the general scope. Take a look at this script:

<?php
    
class person {
        public
$FirstName = "Bill";
        public
$MiddleName = "Terence";
        public
$LastName = "Murphy";
        private
$Password = "Poppy";
        public
$Age = 29;
        public
$HomeTown = "Edinburgh";
        public
$FavouriteColour = "Purple";
    }

    
$bill = new person();

    foreach(
$bill as $var => $value) {
        echo
"$var is $value\n";
    }
?>

Save that script as arrayobject.php and try running it. Your output should be this:

FirstName is Bill
MiddleName is Terence
LastName is Murphy
Age is 29
HomeTown is Edinburgh
FavouriteColour is Purple

Note that the $Password variable is nowhere in sight, because it is marked Private and we're trying to access it from the global scope. If we re-jig the script a little so that the foreach loop is called by the object, we should be able to see the variable:

<?php
    
class person {
        public
$FirstName = "Bill";
        public
$MiddleName = "Terence";
        public
$LastName = "Murphy";
        private
$Password = "Poppy";
        public
$Age = 29;
        public
$HomeTown = "Edinburgh";
        public
$FavouriteColour = "Purple";

        public function
outputVars() {
            foreach(
$this as $var => $value) {
                echo
"$var is $value\n";
            }
        }
    }

    
$bill = new person();
    
$bill->outputVars();
?>

Now the output is this:

FirstName is Bill
MiddleName is Terence
LastName is Murphy
Password is Poppy
Age is 29
HomeTown is Edinburgh
FavouriteColour is Purple

Now that it's the object itself looping through its variables, we can see private variables just fine. Looping through objects this way is a great way to hand-write serialization functions - just remember to put the function inside the object, otherwise private and protected data will get ignored!

 

Next chapter: Object type information >>

Previous chapter: Abstract

Jump to:

 

Home: Table of Contents

Follow us on Identi.ca or Twitter

Username:   Password:
Create Account | About TuxRadar