Have a variable exist in all functions of a class?

Question

I have a small problem - I want to decrease code duplication in my site, and the best way that I can see of doing that is to remove a lot of unnecessary instances of variable setting.

One of the most common is the $baseUrl variable, which contains the http host and php self values, for convenience. However, I have to set it for each function:

class Site
{
function outputPage()
{    
$baseUrl = "http://". $_SERVER['HTTP_HOST'] . rtrim(dirname($_SERVER['PHP_SELF']), '/\\');
}
}

This is then typically included in any links that the site uses:

echo '<a href="' . $baseUrl .'/article/jun/example11/">Example 11</a>';

It's set around six times throughout the class, once per function that needs it - is there any way to set it once and then allow all the functions to access it?

Answer 1

I think you should use a constant for it:

define("BASE_URL", "http://".$_SERVER['HTTP_HOST'].rtrim(dirname($_SERVER['PHP_SELF']), '/\\'));

Then use

echo '<a href="' . BASE_URL .'/article/jun/example11/">Example 11</a>';

It is appropriate to use a constant because the value never changes in the run time of the script. You could also set a class variable for it. Which still will have to be duplicated in every class.

class myClass{
    private $baseURL;
    function __construct()
    {
        $this->baseURL = http://".$_SERVER['HTTP_HOST'].rtrim(dirname($_SERVER['PHP_SELF']), '/\\');
    }
    function speak()
    {
        echo $this->baseURL;
    }
}

Answer 2

Methods of a class can access members of that class.

class Site {

  private $baseurl;

  public function __construct()
  {
    $this->baseurl = "http://www.somesite.com";
  }

  public function hello()
  {
    print "My baseurl is " . $this->baseurl;
  }

}

$site = new Site;
$site->hello(); // My baseurl is http://www.somesite.com

Answer 3

I prefer to define those sorts of things as class constants.

class Settings
{
    const BASE_URL = "http://google.com";
}

Then you can use require_once("settings.php"); anywhere and have access to Settings::Base_URL

Answer 4

You could set it as a class variable, and initialize it in the constructor :

class Site {
    public function __construct() {
        $this->baseUrl = "http://". $_SERVER['HTTP_HOST'] . rtrim(dirname($_SERVER['PHP_SELF']), '/\\');
        var_dump('constructor : ' . $this->baseUrl);
    }
    function outputPage() {    
        // use $this->baseUrl
        var_dump($this->baseUrl);
    }
    protected $baseUrl;
}

And, then, when using the class :

$a = new Site();
$a->outputPage();

You'll get :

string 'constructor : http://tests/temp' (length=31)
string 'http://tests/temp' (length=17)

In some cases, you could also initialize "on the fly" when you're declaring it (on the line with protected, in my example).
But this doesn't work with everything ; you can't call a function there, for instance, if I remember correctly ; you can't concatenate strings either :

class Site {
    function outputPage() {    
        // use $this->baseUrl
        var_dump($this->baseUrl);
    }
    protected $baseUrl = "http://". $_SERVER['HTTP_HOST'] . rtrim(dirname($_SERVER['PHP_SELF']), '/\\');
}

Would give you this error :

Parse error: syntax error, unexpected '.', expecting ',' or ';'

But this :

class Site {
    function outputPage() {    
        // use $this->baseUrl
        var_dump($this->baseUrl);
    }
    protected $baseUrl = "http://www.google.com";
}

Would work -- but it's not as powerful, and you can't really do whatever you might want, this way...

Answer 5

just create a class member with that variable :)

class Site {
  private $baseurl;
  public function __construct() {
    $this->baseurl = "http://". $_SERVER['HTTP_HOST'] . rtrim(dirname($_SERVER['PHP_SELF']), '/\\');
  }
  public function outputPage() {    
    echo $this->baseurl;
  }
}