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PHP shorthand syntax

Quick question. I keep seeing shorthand expressions in libraries around the place, and despite having been a PHP developer for over 3 years, I struggle to quite see how the following would evaluate.

What exactly does the PHP interpreter do with the following shorthand lines of code when it encounters them?

<?php
    defined('foo') OR exit('foo is not defined!');

    $foo AND $this->bar();

I’m guessing that it’ obviously conditional execution – i.e. the second statement won’t get executed unless the first bit is true… but the use of the bitwise operators confuse me a bit.

Can someone elaborate?

Thanks 🙂

Answer 1

Back when I was learning PHP I remember reading the ‘do or die’ style commands and not fully understanding them at the time, the classic example is:

mysql_connect() or die('couldn\'t connect');

Bear in mind that the conditions will only run if they’re required, for example:

if (a == b && b == c)

Here b == c will only be tested if a == b. The same theory applies to or:

if (a == b || b == c)

Now b == c will only be tested if a != b.

In this case you are relying on this order to run a command (exit or $this->bar()) in certain conditions.

Be Aware… exit() is a bad idea in this circumstance – if you exit(‘something went wrong’) there’s nothing anyone can do to hide this error from the user, also it’s likely to issue a 200 OK HTTP status where a 500 Internal Server Error would be much more appropriate, I would consider something more like:

defined('foo') OR throw new Exception('foo is not defined!');

Here you have a chance to either catch the Exception or at least let PHP catch it and issue a 500 status.

Mat