如何从PHP heredoc表达式中扩展静态类变量？

Question

I'm trying to get a static class variable to expand/resolve inside of a HEREDOC expression within a class constructor, but I cannot find a way to make it work. Please see my very simplified example below:

class foo {

  private static $staticVar = '{staticValue}';

  public $heredocVar;

  public function __construct() {
    $this->heredocVar = <<<DELIM
    The value of the static variable should be expanded here: {self::$staticVar}
DELIM;
  }
}

// Now I try to see if it works...
$fooInstance = new foo;
echo $fooInstance->heredocVar;

Which results in the following output:

The value of the static variable should be expanded here: {self::}

Additionally, I've tried various methods to reference the static variable without luck. I'm running PHP version 5.3.6.

---

Edit

As pointed out by Thomas, it is possible to use an instance variable to store a reference to the static variable, and subsequently use that variable inside the HEREDOC. The following code is ugly, but it does work:

class foo {

  private static $staticVar = '{staticValue}';

  // used to store a reference to $staticVar
  private $refStaticVar;

  public $heredocVar;

  public function __construct() {
    //get the reference into our helper instance variable
    $this->refStaticVar = self::$staticVar;

    //replace {self::$staticVar} with our new instance variable
    $this->heredocVar = <<<DELIM
    The value of the static variable should be expanded here: $this->refStaticVar
DELIM;
  }
}

// Now we'll see the value '{staticValue}'
$fooInstance = new foo;
echo $fooInstance->heredocVar;

Answer 1

What about this answer?

I would set $myVar = self::$staticVar; and then use $myVar in the HEREDOC code.