RE: [PHP] PHP_SELF Undefined

On Tue, 2002-02-19 at 05:14, Ford, Mike [LSS] wrote: > > -----Original Message----- > > From: Matt [mailto:matt@epooch.com] > > Sent: 18 February 2002 23:30 > > To: Lars Torben Wilson > > > > > $foo = "This page is $_SERVER[PHP_SELF]"; [snip] > > Can you expand on why the first option isn't generally > > acceptable? > > Another reason, as I understand it (and I'm sure Torben will correct > me if I'm wrong!), is that in the version without quotes, PHP_SELF is taken as the name of a constant -- which, as it happens to be undefined, PHP very kindly assumes you intended to be the equivalent string 'PHP_SELF'. This is bad for two reasons: (1) the PHP compiler is doing avoidable extra work to get the desired result; (2) if you just happen, at a later date, to define a constant of that name, your result will suddenly be wrong (unlikely with PHP_SELF, I admit, but less so with something like, say, MAX_SIZE). Even though this is only a theoretical danger of low probability, the principles of good defensive programming would suggest that you nonetheless avoid it with a vengeance!! > > Cheers! > > Mike You're very right, but even worse than constant collisions are the keyword collisions, as far as WTF factor goes: <?php $array('default' => 'Select an option', 'option1' => 'First option', 'option2' => 'Second option'); echo $array[default]; // Parse error. ?> This one has come up a number of times. -- Torben Wilson <torben@php.net> http://www.thebuttlesschaps.com http://www.hybrid17.com http://www.inflatableeye.com +1.604.709.0506