PHP - passing variables to classes

Question

I trying to learn OOP and I've made this class

class boo{

  function boo(&another_class, $some_normal_variable){
    $some_normal_variable = $another_class->do_something(); 
  }

  function do_stuff(){
    // how can I access '$another_class' and '$some_normal_variable' here?
    return $another_class->get($some_normal_variable);
  }

}

and I call this somewhere inside the another_class class like

$bla = new boo($bla, $foo);
echo $bla->do_stuff();

But I don't know how to access $bla, $foo inside the do_stuff function

(reference) Classes and Objects Basics

Gordon
– Gordon

2011-02-02 17:45:24 +00:00
Commented Feb 2, 2011 at 17:45 — Gordon
– Gordon, Commented Feb 2, 2011 at 17:45
Read about $this on docs.php.net/this!

rik
– rik

2011-02-02 17:47:22 +00:00
Commented Feb 2, 2011 at 17:47 — rik
– rik, Commented Feb 2, 2011 at 17:47

nyedidikeke · Accepted Answer · 2017-09-06 07:52:51Z

12

<?php
class Boo
{

    private $bar;

    public function setBar( $value )
    {
        $this->bar = $value;
    }

    public function getValue()
    {
        return $this->bar;
    }

}

$x = new Boo();
$x->setBar( 15 );
print 'Value of bar: ' . $x->getValue() .  PHP_EOL;

Please don't pass by reference in PHP 5, there is no need for it and I've read it's actually slower.

I declared the variable in the class, though you don't have to do that.

edited Sep 6, 2017 at 7:52

nyedidikeke

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answered Feb 2, 2011 at 17:46

Logan Bailey

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3 Comments

Mikhail Over a year ago

Like @Logan said - Bottom line is if you want to save some information - then you need to save it in the local class.

Rafe Kettler Over a year ago

I wouldn't make the blanket statement "don't pass by reference in PHP5." Maybe not for composition, but what if you wanted to modify an array in place? Passing by reference has its advantages.

zzzzBov Over a year ago

you should probably say "there is rarely a need for it". In most cases it is unnecessary.

ircmaxell · Accepted Answer · 2011-02-02 17:46:47Z

Ok, first off, use the newer style constructor __construct instead of a method with the class name.

class boo{

    public function __construct($another_class, $some_normal_variable){

Second, to answer your specific question, you need to use member variables/properties:

class boo {
    protected $another_class = null;
    protected $some_normal_variable = null;

    public function __construct($another_class, $some_normal_variable){
        $this->another_class = $another_class;
        $this->some_normal_variable = $some_normal_variable;
    }

    function do_stuff(){
        return $this->another_class->get($this->some_normal_variable);
    }
}

Now, note that for member variables, inside of the class we reference them by prefixing them with $this->. That's because the property is bound to this instance of the class. That's what you're looking for...

Rafe Kettler · Accepted Answer · 2011-02-02 17:54:49Z

3

In PHP, constructors and destructors are written with special names (__construct() and __destruct(), respectively). Access instance variables using $this->. Here's a rewrite of your class to use this:

class boo{

  function __construct(&another_class, $some_normal_variable){
    $this->another_class = $another_class;
    $this->some_normal_variable = $another_class->do_something(); 
  }

  function do_stuff(){
    // how can I access '$another_class' and '$some_normal_variable' here?
    return $this->another_class->get($this->some_normal_variable);
  }

}

edited Feb 2, 2011 at 17:54

answered Feb 2, 2011 at 17:46

Rafe Kettler

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4 Comments

zzzzBov Over a year ago

"For backwards compatibility, if PHP 5 cannot find a __construct() function for a given class, it will search for the old-style constructor function, by the name of the class. Effectively, it means that the only case that would have compatibility issues is if the class had a method named __construct() which was used for different semantics." - PHP Constructors and Destructors. Using the new syntax is still a good idea, as backwards compatibility may be dropped in the future.

Rafe Kettler Over a year ago

@zzzzBov right, I would never tell someone to start using something that was deprecated. IMO this style is more clear.

zzzzBov Over a year ago

I was just trying to add clarity as to why @Alexandra's code works (for the constructor that is).

JasonDavis Over a year ago

What people still use PHP < 5...that would be crazy!

Foo Bah · Accepted Answer · 2011-02-02 17:46:52Z

1

You need to capture the values in the class using $this:

$this->foo = $some_normal_variable

answered Feb 2, 2011 at 17:46

Foo Bah

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