PHP - Pass a variable to a function, even if undefined

Question

I have the following snippet:

// Some post is made and I have access to it using Input::get('name_of_field');
if (Input::has('optionalField'))
{
    $thisVariable = myMagicalFunction();
}

// more operation
// being performed

ultimateFunction($thisVariable);

return true;

As you can see, $thisVariable may sometimes not be set, and so the ultimateFunction($thisVariable) may sometimes return error saying the variable is undefined. I can of course use

if (isset($thisVariable)) ultimateFunction($thisVariable);

But is there a way to force pass the variable anyhow without checking if it is set? I will then check if it is set inside ultimateFunction.

vascowhite · Accepted Answer · 2014-07-12 21:54:17Z

4

The simplest way is to just declare the variable before it is used:-

$thisVariable = null;
if (Input::has('optionalField'))
{
    $thisVariable = myMagicalFunction();
}

// more operation
// being performed

ultimateFunction($thisVariable);

return true;

answered Jul 12, 2014 at 21:54

vascowhite

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2 Comments

Kousha Over a year ago

I know, I wanted to skip that one line! I guess I shouldn't then.

Marcin Nabiałek Over a year ago

@Kousha you definitelly shouldn't. The best approach is to create PHP code that have no warnings or notices.

degenerate · Accepted Answer · 2014-07-12 21:24:39Z

0

You can suppress the error with @, so:

ultimateFunction(@$thisVariable);

But it's better to check first. I personally use @ all the time. It's bad practice.

answered Jul 12, 2014 at 21:24

degenerate

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1 Comment

vascowhite Over a year ago

I down voted this for recommending the use of error suppression. It is bad practice and worse advice.

smcjones · Accepted Answer · 2014-07-12 21:30:20Z

0

It is at best a hack to suppress your error this way. You are ignoring warnings and writing code which is not optimized. Even though it saves you a bit of time, I strongly suggest you avoid doing this.

Ideally, create a service container for $_GET and $_POST which performs this check for you. It can return null if it does not exist.

Alternatively, a procedural answer is something like this:

function formGet($input) {
    if(isset($_GET[$input])) {
        return $_GET[$input];
    }
    return false;
}

Now you can simply input your data using formGet($input).

answered Jul 12, 2014 at 21:30

smcjones

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Comments

Kubo2 · Accepted Answer · 2014-07-12 21:44:34Z

-1

It is possible to use PHP's error control operator (at-sign):

// ...
ultimateFunction(@$thisVariable);

There will be null force-passed as the ultimateFunction's first argument and inside function you will be able to normally check with isset() or empty() whether variable was passed.

But if it is possible, that does not mean you should use it. As @degenerate said too, it is really bad practice, because PHP parser expands the code above using @ operator to code snippet like following:

$old = error_reporting(0);
ultimateFunction($thisVariable);
error_reporting($old);

Additionally use of this operator might slower the application.

edited Jul 12, 2014 at 21:44

answered Jul 12, 2014 at 21:27

Kubo2

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6 Comments

vascowhite Over a year ago

I down voted this for recommending the use of error suppression. It is bad practice and worse advice.

Kubo2 Over a year ago

@vascowhite I have edited the post adding mention about it. Don't it additionally slower application, too?

vascowhite Over a year ago

Pointing it out as bad practice does not make the recommendation to use it any better.

Kubo2 Over a year ago

@vascowhite And how can I edit the post to not be a recommendation of best practice? May I prepend Use with You can?

vascowhite Over a year ago

In my opinion it should not be offered as a solution at all as it isn't really. The error is still there, it is just suppressed. I think that this answer and the other saying the same should be deleted.

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