Alternative to the 'or' keyword in PHP

Question

Right now I have the following code:

stream_wrapper_register("var", "VariableStream")
    or die("Failed to register protocol");

And I want to do extra stuff before the die in case the function fail. So it raised that question :

How does the 'or' keyword works exactly ?

In many SO questions or answer, I've seen people creating a function, like this :

function doStuff() {
    header('HTTP/1.1 500 Internal Server Error');
    die("Failed to register protocol");
}

stream_wrapper_register("var", "VariableStream")
    or doStuff();

... but this is kind of unpractical in an Object Oriented context as I don't really want to create a method for that in my object, and I can't yet use closure.

So for now, I've used this code, but I'm not sure that it will have the exact same behaviour :

if (!stream_wrapper_register("var", "VariableStream") {
    header('HTTP/1.1 500 Internal Server Error');
    die("Failed to register protocol");
}

Answer 1

The statement with "or" works, because the PHP-Interpreter is quite intelligent: Because a connection of "or"'s is true, if the first of them is true, it stops executing the statement when the first one is true.

Imagine following (PHP)code:

function _true()  { echo "_true";  return true;  }
function _false() { echo "_false"; return false; }

now you can chain the function calls and see in the output what happens:

_true() or _true() or _true();

will tell you only "_true", because the chain is ended after the first one was true, the other two will never be executed.

_false() or _true() or _true();

will give "_false_true" because the first function returns false and the interpreter goes on.

The same works with "and"

You can also do the same with "and", with the difference that a chain of "and"'s is finished, when the first "false" occurres:

_false() and _true() and _true();

will echo "_false" because there the result is already finished an cannot be changed anymore.

_true() and _true() and _false();

will write "_true_true_false".

Because most of all functions indicate their success by returning "1" on success and 0on error you can do stuff like function() or die(). But some functions (in php quite seldom) return "0" on succes, and != 0 to indicate a specific error. Then you may have to use function() and die().

Answer 2

a or b

is logically equivalent to

if (!a) {
    b
}

So your solution is fine.

Answer 3

It's exactly the same since stream_wrapper_register() returns a boolean value.

Answer 4

The two syntaxes are equivalent, and it's just a matter of coding style/preference as to which one you use. Personally, I don't like <statement> or die(...), as it seems harder to read in most circumstances.