Wednesday, January 14. 2004

I don't know about PHP 4.3.x (I haven't tested).. but in PHP 5 the following script is completely valid:


<?php

    class weird {

          var $myvar;
    
          function __construct() {

            $myvar = "Z";
            $this->myvar = "A";
            $this->$myvar = "B";
            $this->${'myvar'} = "C";
            $this->${'$myvar'} = "D";

            echo 'this->myvar: '.$this->myvar."\n";
            echo 'this->$myvar: '.$this->$myvar."\n";
            echo 'this->${\'myvar\'}: '.$this->${'myvar'}."\n";
            echo 'this->${\'$myvar\'}: '.$this->${'$myvar'}."\n";
            echo 'this->$$$$$$$myvar: '.$this->$$$$$$$myvar."\n";
            echo 'this->$$$$$$${\'$$$myvar\'}: '.$this->$$$$$$${'$$$myvar'}."\n";                    
         }
    }

    new weird();
?>




Not only is it valid, but the output is also interesting:


this->myvar: A
this->$myvar: C
this->${'myvar'}: C
this->${'$myvar'}: D
this->$$$$$$$myvar: D
this->$$$$$$${'$$$myvar'}: D



If you remove the declaration of the local $myvar in the constructor you get:


this->myvar: A
this->$myvar: D
this->${'myvar'}: D
this->${'$myvar'}: D
this->$$$$$$$myvar: D
this->$$$$$$${'$$$myvar'}: D


I don't *think* this is a bug, from what I understand of the way the engine works. However, it is quite odd isn't it? Here's something that's even more interesting -- did you know you *can* define a variable that starts with a
number?


<?php
    ${1} = "Hi";
    echo "${1}\n";
?>




In fact, you can put just about any expression you want in between the ${ } and create a variable (including NULL). Of course, it is strongly recommended you EVER do such things in a real PHP script -- I just thought I'd share.