Why this expression return error and how can I resolve?

Question

This code:

if(!empty(trim($_POST['post']))){ }

return this error:

Fatal error: Can't use function return value in write context in ...

How can I resolve and avoid to do 2 checks ( trim and then empty ) ?

I want to check if POST is not only a blank space.

Did you actually read [the documentation page](http://php.net/manual/en/function.empty.php)? It clearly states that only variables work with `empty()` in PHP < 5.5 — nice ass, May 02 '13 at 14:41
Why not just `trim($_POST['post']) !== ""`? `trim` `$_POST` values can only be strings, and `trim` will cast to string anyway. — cmbuckley, May 02 '13 at 14:44
@OneTrickPony the funniest thing is what sample in warning use exact trim function to display problem:) — Narek, May 02 '13 at 14:46

score 3 · Answer 1 · answered May 02 '13 at 14:42

3

you cant use functions inside isset , empty statements. just assign the result of trim to a variable.

$r = trim($_POST['blop']);

if(!empty($r))....

edit: Prior to PHP 5.5

answered May 02 '13 at 14:42

mpm

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score 2 · Answer 2 · answered May 02 '13 at 14:42

2

if (trim($_POST['post'])) {

Is functionally equivalent to what you appear to be trying to do. There's no need to call !empty

answered May 02 '13 at 14:42

AD7six

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score 2 · Answer 3 · answered May 02 '13 at 14:47

2

if (trim($_POST['post']) !== "") {
    // this is the same
}

answered May 02 '13 at 14:47

cmbuckley

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score 1 · Accepted Answer · answered May 02 '13 at 14:42

1

In the documentation it actually explains this problem specifically, then gives you an alternate solution. You can use

trim($name) == false.

answered May 02 '13 at 14:42

christopher

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Quite why the PHP documentation even recommends this solution is beyond me. Why promote unnecessary type coercion? (I'm not saying it's slower, but it's the principle of the matter!) – cmbuckley May 02 '13 at 23:04
I'm not sure, but it is the shortest solution. – christopher May 03 '13 at 09:18
`!trim($name)` is shorter :-) And for that matter, so is `trim($name) === ''`! – cmbuckley May 11 '13 at 13:05

score 0 · Answer 5 · answered May 02 '13 at 14:52

In PHP, functions isset() and empty() are ment to test variables.

That means this

if(empty("someText")) { ... }

or this

if(isset(somefunction(args))) { ... }

doesn't make any sence, since result of a function is always defined, e.t.c.

These functions serve to tell wether a variable is defined or not, so argument must me a variable, or array with index, then it checks the index (works on objects too), like

if(!empty($_POST["mydata"])) {
    //do something
} else {
    echo "Wrong input";
}

Why this expression return error and how can I resolve?

5 Answers5