I just found a nice (or lets say not so nice) unexpected behavior in PHP. Apparently anything goes with constructors.

Calling a constructor that hadn’t been defined did not throw any kind of exception, error, warning, whatsoever.

So the following example executes:

class TestClass {
  public function testFunction() {
    return "Hello World!";
  }
}
 
$testClass = new TestClass ("blabla"); // should report an error
echo $testClass->testFunction(); // Hello World

Update: Apparently there is a rationale behind this: the PHP function func_get_arg() allows shell style retrieval of function arguments.