The following example doesn't work, but is listed in the documentation as being valid:

<?php
class DateTime {
  
  function DateTime() {
      // empty constructor
  }

  function now() {
      return date("Y-m-d H:i:s");
  }
}

class Report {
  var $_dt = new DateTime();
  // more properties ...

  function Report() {
      // initialization code ...
  }

  function generateReport() {
      $dateTime = $_dt->now();
      // more code ...
  }

  // more methods ...
}

$rep = new Report(); 
?>

This returns the error:

Parse error: parse error, unexpected T_NEW in test.php on line 14


I have tried this with other classes and basically it seems that you cannot default a class property to an instatiated class unless through the constructor.  This is contrary to the documentation.