New to Object Oriented PHP

particlepattern

Hello guys. I have tried everything I could think of to get a method to return an array and its just not working. I've searched the internet for things like "return an array from a method" and "declare an array" but I am just not getting anywhere that way. I even made a separate script, the sole function of which is to return an array from the database - to remove all of the other code so its easier to figure out where I went wrong. I figure one of you guys will probably see my mistake immediately:

<?php
require_once('/* Database Connection */');

class return_array {

public $session_array = array();
var $website_pdo = NULL;
var $website_connection = NULL;
var $prepared_statement = NULL;
var $mysql_statement = NULL;

function set_session_array() {
    // Neither of these makes it work:
    $this->session_array = $session_array;
    $this->session_array = new ArrayObject();
}

function get_session_array($session_id,
                           $session_array = NULL) {

    // I want to get something out of the database:

    $website_pdo = new website_pdo;
    $website_connection = $website_pdo->website_connection();

    $mysql_statement = "SELECT * FROM sessions
                        WHERE session_id = :session_id";

    $prepared_statement = $website_connection->prepare($mysql_statement);

    $prepared_statement->bindParam(":session_id", $session_id);

    $prepared_statement->execute();

    $session_array = $prepared_statement->fetch(PDO::FETCH_ASSOC);

    // Even doing this does not work:
    /* $session_array = NULL;
    $session_array[0] = 'a';
    $session_array[1] = 'b';
    $session_array[2] = 'c'; */

    // It prints fine from inside the object
    echo '<br /><br /> From Inside the Object: ';
    print_r($session_array); 
    echo '<br /><br />';

    return $this->$session_array;

    $website_connection = NULL;
}
}

$return_array = new return_array;

// Does not print outside the object:
echo '<br /><br /> <h1>Return Array Results, Attempt 1:</h1> ';
$return_array->get_session_array('b181741a4c233fb05b0d1008aa7ae1fb');
print_r($return_array);

// This does not work either:
echo '<br /><br /><h1>Return Array Results, Attempt 2:</h1> ';
print $return_array->get_session_array("b181741a4c233fb05b0d1008aa7ae1fb");
echo '<br /><br />';

?>

This is the result I am getting:

Notice: Array to string conversion in (file paths)
Notice: Undefined property: return_array::$Array
return_array Object ( [session_array] => Array ( ) [website_pdo] => [website_connection] => [prepared_statement] => [mysql_statement] => )

bradgrafelman

Well for one, this method:

    function set_session_array() { 
        // Neither of these makes it work: 
        $this->session_array = $session_array; 
        $this->session_array = new ArrayObject(); 
    }

first tries to use an undefined variable $session_array.

Next, your get_session_array/b method never assigns anything to the session_array property of the object instance. Instead, you use a local variable called $session_array and then do something that doesn't make sense:

return $this->$session_array;

Here, $session_array contains the return value of the call to the method $prepared_statement->fetch(PDO::FETCH_ASSOC). You then try to use that value as the name of a property (e.g. $this->propertyName).

Either return the local variable you create inside that method, or first store the value of that local variable in the property that you're almost doing now (just with an erroneous $ in there, I'm guessing).

spufi

Also, return_array is more of a function name versus a class name since it is implying some sort of action. I would name the class something like Session_Array and then name the functions get() and set().

particlepattern

Brad,

Thanks for your response.  I see now that my root problem is that the reading material I have been learning from have been giving me an incomplete idea of the concepts behind things.  Do you know what book would be good for learning to write object oriented PHP?

I have some specific questions, too, if you're willing to look at them:

bradgrafelman;10995155 wrote:
Well for one, this method:
    function set_session_array() { 
        // Neither of these makes it work: 
        $this->session_array = $session_array; 
        $this->session_array = new ArrayObject(); 
    } 
first tries to use an undefined variable $session_array.

The set methods confuse me because if they do not find variables declared within the same class, then I suppose that means those variables need to be passed to them... but I am not calling all of my get methods, and yet they seem to be working (in other scripts).  In procedural, if I don't call a function, it does nothing, and if I do not pass the variable in my function call, it does not receive the variable.  I guess that methods will receive a property if it is in the class, even if the method is not called anywhere and therefore the variable is not passed to it in a call, but it does have to be put into the parentheses.  Is that right?  I think I may be unaware of a concept here.  If there is something you can say about this that would clarify a concept that would be appreciated.

bradgrafelman;10995155 wrote:
Next, your get_session_array/b method never assigns anything to the session_array property of the object instance. Instead, you use a local variable called $session_array and then do something that doesn't make sense:
return $this->$session_array;
Here, $session_array contains the return value of the call to the method $prepared_statement->fetch(PDO::FETCH_ASSOC). You then try to use that value as the name of a property (e.g. $this->propertyName). Either return the local variable you create inside that method, or first store the value of that local variable in the property that you're almost doing now (just with an erroneous $ in there, I'm guessing).

Oh... Sigh.  I hate how a tiny syntax mistake like that can ruin the whole script.  I will be a lot more on top of this particular problem of using the $ in front of a property name now that this has been pointed out.  

You know, my first attempt at this did return $session_array straight up.  However, that results in an object being returned, not the database results I wanted.  This is why I switched to trying to assign that data to a property.  The way you're wording things is making me suspect that shoving a data array into a property like that and returning it might be considered an awkward way of doing things.  However, I cannot seem to get the database data out of this method using the $session_array variable (return $session_array;) - it just outputs a textual representation of my object...   So, if you don't mind, which way of doing things is considered most sane, and if it is by using return $session_array; then what concept am I missing here, which is causing my code to return an object instead of the data?

particlepattern

spufi;10995199 wrote:
Also, return_array is more of a function name versus a class name since it is implying some sort of action. I would name the class something like Session_Array and then name the functions get() and set().

As I said "I even made a separate script ... so its easier to figure out where I went wrong." In other words, this script is not going to be a permanent part of the website. I may as well have named it foo. But you're right. Good naming conventions are important. I have been naming my objects objecty-sounding things. The name of the original class, not shown here, is safer_session. Do you know a good source where I can learn everything I need to know about object oriented naming conventions?

spufi

While written for Java, The Elements of Java Style covers how to format OOP programming code and is worth a look at. It's a small book just like the book it's based off of so it's easy to carry around and have as a reference. I would look for a used copy as I'm sure you could get one for dirt cheap.

Derokorian

PHP Objects, Patterns, and Practice by Matt Zandstra is great for learning OOP. I would highly recommend this book (I have it myself)

NogDog

Derokorian;10995254 wrote:
PHP Objects, Patterns, and Practice by Matt Zandstra is great for learning OOP. I would highly recommend this book (I have it myself)

sneakyimp

Derokorian;10995254 wrote:
PHP Objects, Patterns, and Practice by Matt Zandstra is great for learning OOP. I would highly recommend this book (I have it myself)

Nice. Someone gave me this book and it's been sitting on my shelf. I guess I'll have to read it now.