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[RESOLVED] PHP version of "undefined || literal"

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Dec 22.2009

In JavaScript, when I’m not sure if a variable is defined, I can say

[CODE]alert(myVar || “Something else”)[/CODE]

If the variable is undefined, it will obviously return “Something else”.

In PHP, I have been using isset() and the ternary operator (??

[code=php]echo isset($myVar) ? myVar : ‘Something else’;[/code]

This seems kind of redundant, and I was hoping there was something similar in PHP.

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9 Comments(s) ↴

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@jamesbcox1980authorDec 22.2009 — I guess maybe what I should be looking at is how to declare undefined in PHP. I forgot that I usually insert "var undefined;" in my JS template to make this work. I guess I need to do the same in PHP... but declaring variables is a little different.
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@NogDogDec 22.2009 — Offhand I don't know of a terser way than the tenary operator for this sort of thing.

As far as "defining" a variable as undefined, you can set it to null, which isset() will treat as not set.
[code=php]
var_dump(isset($var)); // false
$var = null;
var_dump(isset($var)); // false
$var = false;
var_dump(isset($var)); // true
[/code]
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@jamesbcox1980authorDec 22.2009 — Well, I'm not looking to define a variable as undefined, I'm trying to set undefined to null by declaring it.

In JavaScript,[CODE]var undefined;[/CODE] takes a reserved word, undefined, and defines it, so that whenever a variable is undefined and gets called, it will return "undefined" instead of throwing an undefined variable error. This way, you can use the "||" operator instead of using the whole typeof() thing. It's not a strict standards compliant method, but it works and makes for easier error handling. Even jQuery uses it.
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@NogDogDec 22.2009 — Nope, nothing like that in PHP that I've ever seen.
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@MindzaiDec 22.2009 — what happens when myVar is false? Or some other correct value which evaluates false?
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@KorDec 22.2009 — The PHP's Boolean operators [I]always[/I] return a Boolean value... as opposed to other languages that return the value of the last evaluated expression.

But you may do something tricky like:

[code=php]
$echo=$myVar or $echo="something else";
echo "$echo";
[/code]
It will work with a notable exception: when $myVar=0. In this case the assignment $echo=$myVar is evaluated as Boolean [B]false[/B].

Or you may simplify the ternary operator like this:
[code=php]
echo ($myVar?$myVar:"something else");
[/code]
But, again, $myVar can have any value except 0, because 0 is evaluated as Boolean false.
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@MindzaiDec 22.2009 — 
But, again, $myVar can have any value except 0...[/QUOTE]

or "", or "0", or an empty array, or null etc. This technique seems dodgy enough in javascript! Just use isset() to see if a variable has been defined.
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@KorDec 22.2009 — or "", or "0", or an empty array, or null etc. This technique seems dodgy enough in javascript! Just use isset() to see if a variable has been defined.[/QUOTE]
I agree. So, [B]jamesbcox1980[/B], the answer is no. As I said, php always return a Boolean value on Boolean operators.
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@jamesbcox1980authorDec 22.2009 — Ok, thanks guys
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