declaring variables in classes using PHP

Question

Fairly new to classes in PHP, so bear with me.

class processRoutes
    {   
        //Next line works
        private $doc = "works as as string";
        //Next line does not work, "Parse error: syntax error, unexpected T_NEW"
        private $doc = new SimpleXMLElement('routingConfig.xml', null, true);
        private function getTablenames()
        {
            //do stuff  
        }
    }

I'm trying to ultimately utilize the SimpleXMLElement object within my class, among several private functions. What is the correct method for going about this, and why doesn't my current method work?

Answer 1

You need to do this in your constructor, as this can't be evaluated at this stage of script parsing. 'Simple' values, as strings, bools and numeric values will work though.

class processRoutes
{   
  //Next line works
  private $doc = "works as as string";

  private $doc;

  public function __construct()
  {
     $this->doc = new SimpleXMLElement('routingConfig.xml', null, true);
  }

  // ....
}