Question

I’m really new to OOP. I’m even not a newbie – I’m noob. So. I want to transfer my pseudo-CMS from “normal” programming, into OOP programming system. And so:

private static $dsn = DB_TYPE.':host='.DB_HOST.';dbname='.DB_NAME;

What here causes problem? Usage of constraints? I don’t know. My editor (aptana studio) shows error after 1 constant. Thanks

Edit:

Thanks for fast reaction. I’ll do it in contructor.

Edit2:

But what if i want to use singleton? How to pass arguments to contructor?

Answer 1

See the documentation:

This declaration may include an initialization, but this initialization must be a constant value–that is, it must be able to be evaluated at compile time and must not depend on run-time information in order to be evaluated.

You cannot concatenate strings when defining class properties.

Example from the documentation (for completness):

<?php
class SimpleClass
{
   // invalid property declarations:
   public $var1 = 'hello ' . 'world';
   public $var2 = <<<EOD
hello world
EOD;
   public $var3 = 1+2;
   public $var4 = self::myStaticMethod();
   public $var5 = $myVar;

   // valid property declarations:
   public $var6 = myConstant;
   public $var7 = array(true, false);

   // This is allowed only in PHP 5.3.0 and later.
   public $var8 = <<<'EOD'
hello world
EOD;
}

?>

---

As you switch to OOP anyway you should not use constants. Pass those values to the constructor of your class:

public function __construct($db_type, $db_host, $db_name) {
    self::$dsn = $db_type.':host='.$db_host.';dbname='.$db_name;
}