CODEWITHSUNDEEP
php
Daniel Scocco
Daniel Scocco

Reputation: 7266

PHP isset() redundant in this context?

I am going through the "Head First PHP & MySQL" book right now, and on many parts of the book there are code snippets used to process HTML forms. They start like this:

if (isset($_POST['submit'])){
...
}

The if clause is used to detect if the form has been submitted already or not. Being used to programming in C mostly, I find that construct redundant and annoying (and I also don't think it helps code readability for experienced programmers). I would rather write it as:

if ($_POST['submit']){
    ...
}

Question: Is there some other reason to use isset() in this context that I might be missing? Would my version of the snippet be considered non-idiomatic PHP? What about in other contexts, can you give me an example of when isset() might be useful?

Upvotes: 2

Views: 193

Answers (4)

drew010
drew010

Reputation: 69957

One of the biggest reasons I can think of is because of PHP's error_reporting and display_errors setting.

Let's say that error_reporting is set to E_ALL and display_errors is turned on.

If you tried to do something like: if ($array['iDontExist'] == false) the code will run as expected, since the variable isn't set, it will evaluate to boolean false. The side effect however, is that PHP will emit a notice saying the variable $array['iDontExist'] does not exist. The more you have this, the more likely random notices will be spammed all over the output.

I find a LOT of production systems have error reporting turned on which would result in this unwanted behavior. If display_errors is turned off, the messages won't show up in the browser, but if error_reporting is set to track notices, the error_log will contain all of the notices about undefined variables, which is also an annoyance.

Upvotes: 1

entropid
entropid

Reputation: 6239

Well, if $_SERVER doesn't have the submit key, the second block would throw an E_NOTICE (Undefined index), therefore you should use isset() if you want to check if that key exists and is not null (or, alternatively, array_key_exists(), which just check for the existence).

Additionally, if you also want to check the content of the variable (for example, if it's set to false or 0), I'd suggest to use the !empty() (note the negation with !) function instead of isset().

Upvotes: 1

dpk2442
dpk2442

Reputation: 701

Check out this page for more information about isset()

http://php.net/manual/en/function.isset.php

Upvotes: 2

ceejayoz
ceejayoz

Reputation: 180014

There are situations where a variable is NULL, 0, or FALSE. They'd fail the if() {} comparison, but they are set.

Using isset() also avoids a notice about an undefined variable if your error_reporting settings include E_NOTICEs.

Upvotes: 9

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