What does "or" in php mean?

Question

Possible Duplicate:
PHP - and / or keywords

I saw several bits of PHP code using or in a way I was unfamiliar with. For example:

fopen($site,"r") or die("Unable to connect to $site");

Is this equal to this ||?

Why would you use this instead of a try catch block? What will cause the program run the or die()?

*(related)* [What does that symbol mean in PHP](http://stackoverflow.com/questions/3737139/reference-what-does-this-symbol-mean-in-php) — Gordon, Apr 21 '11 at 17:30
You know, I don't think this is a duplicate. It's really a question about what "expression or die" means. — John Saunders, Apr 21 '11 at 20:14

score 9 · Answer 1 · answered Apr 21 '11 at 17:08

9

It is for the most part, but...

The reason for the two different variations of "and" and "or" operators is that they operate at different precedences.

See http://php.net/manual/en/language.operators.logical.php

answered Apr 21 '11 at 17:08

Daniel A. White

187,200
47
362
445

score 2 · Answer 2 · answered Apr 21 '11 at 17:09

2

or is equal to || except that || has a higher presedense than or.

Reference:

http://www.php.net/manual/en/language.operators.precedence.php

answered Apr 21 '11 at 17:09

Mike Lewis

63,433
20
141
111

score 1 · Answer 3 · edited Apr 21 '11 at 17:27

or has an other precedence. The concrete statement is little trick with boolean operators. Like in a common if-test-expression the second part is only executed, if the first is evaluated to false. This means, if fopen() does not fail, die() is not touched at all.

However, try-catch only works with Exceptions, but fopen() doesnt throw any.

Today something like this is "not so good" style. Use exceptions instead of hard abortion

if (!($res = fopen($site, 'r'))) throw new Exception ("Reading of $site failed");

GAgnew · Answer 4 · 2011-04-21T17:16:35.893

0

or die happens with the first command fails.

It is similar to a try catch, but this is more direct approach.

Note that this is a classical test:

fopen($site,"r") or die("Unable to connect to $site");

Only if fopen($site,"r") returns false, will the second half of the test be run: 'die('error')'.

Same is if(a || b); b is only run if a returns false.

Die in PHP is the same as exit(); http://www.php.net/manual/en/function.exit.php

Stops execution of the current script entirely, and prints out the error message.

edited Apr 21 '11 at 17:16

answered Apr 21 '11 at 17:10

GAgnew

3,847
3
26
28

1

Its not similar to `try-catch`. – KingCrunch Apr 21 '11 at 17:16
_Similar_ to try catch as in, it trys the first statement, and on false, executes the second. Or on true, does not execute the second statement, or 'catch'. I was commenting on the posters question 'Why would you use this instead of a try catch block? ' Where as try/catch is on error, this is on boolean. – GAgnew Apr 25 '11 at 05:38

score -1 · Answer 5 · answered Apr 21 '11 at 17:08

-1

Yes it equals ||

In this case it is explicitly stopping the execution of the page and printing that error message.

answered Apr 21 '11 at 17:08

Gho5t

1,060
1
12
23

1

It's not equal... It has a different precedence... – Macmade Apr 21 '11 at 17:10

What does "or" in php mean?

5 Answers5