using undefined Variable in php function

Question

I'm new to PHP and working on script that may have undefined variable and I have two ways to handle this, my question is what is the best way.

Variable $_GET['page'] can be sometimes defined and sometimes undefined.

the first way I check with isset() and if:

if(isset($_GET['page'])){
    $sql.=limitrows($_GET['page'],10);
}else{
    $sql.=limitrows(1,10);
}

the second way I just write the function and using @ remove the error and handle the isset() inside the function

 function limitrows($page=1, $rows=10){
       if (isset($page)==false or $page<=0 ){
         $page=1;
       }
  }

 $sql.=@limitrows($_GET['page'],10);

the second way make my code much cleaner and I do all the dirty work inside the function but it show error and I have to @. What is the best way?

Keep always the code in control then use isset and dontt mask error ,... (never...) but eventually manage the error with try catch — ScaisEdge
– ScaisEdge, Commented May 24, 2016 at 19:50
chris85 this is not full function I just put only what I asked and this is how should I use '@' but if needed I can write what it return. — Meir
– Meir, Commented May 24, 2016 at 20:02
the code work fine the only problem is that how to handle when I have undefined variable. :) — Meir
– Meir, Commented May 24, 2016 at 20:10

Don't Panic · Accepted Answer · 2016-05-24 20:07:54Z

3

One possibility is to use a filter function to access the GET parameter.

$page = filter_input(INPUT_GET, 'page', FILTER_SANITIZE_NUMBER_INT);

With this approach, $page will always be set, so you won't need to worry about undefined index warnings. (If 'page' is not a key in $_GET, filter_input will return null.)

Then, when you need to use $page later, checking it is simpler:

function limitrows($page, $rows=10) {
    if (!$page) $page = 1;   // assuming you don't have a page 0, or
    // if ($page === null) $page = 1; // if you DO have a page 0
    // ... 
}

answered May 24, 2016 at 20:07

Don't Panic

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Comments

Chris Baker · Accepted Answer · 2016-05-24 20:18:19Z

2

Another approach is to use array_key_exists to check for the existence of an array key. You can use an if statement, or shorten it with a ternary.

// with if
$page = 1;
if (array_key_exists('page', $_GET) === true) {
    $page = $_GET['page'];
}

// with ternary
$page = array_key_exists('page', $_GET) === true ? $_GET['page'] : 1;

Do not use the @ error suppression operator. It is a bad practice to get into, 99.99% of the time you want to see all errors in all situations.

The "best way" in coding is a combination of opinion, established code style, and industry best practices. Generally speaking, one should use the right functions for the job (in this case, array_key_exists or filter_input as indicated in another answer), not use error handling, suppression, or exceptions for normal code flow, and be explicit/verbose rather than trying for the shortest code. You might be able to condense something into 1 line rather than 3, but to what end? All it does is increase the specific complexity of any given part of your code, making it harder for others (and yourself!) to understand and maintain in the future.

In terms of where to do what, gather your arguments outside the function AND validate the arguments inside the function.

Documentation/More Reading

array_key_exists - http://php.net/manual/en/function.array-key-exists.php
Ternary operator - http://php.net/manual/en/language.operators.comparison.php
PHP The Right way, see: "Inline Error Suppression" - http://www.phptherightway.com/

answered May 24, 2016 at 20:18

Chris Baker

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1 Comment

Don't Panic Over a year ago

"gather your arguments outside the function AND validate the arguments inside the function" I strongly agree. No need to limit the usability of your function by tying it to $_GET or some other specific source.

Jinjubei · Accepted Answer · 2016-05-24 19:48:17Z

0

Use the ternary operator

$sql.=@limitrows(isset($_GET['page'])?$_Get['page']:1,10);

format [logic]?[true]:[false]

answered May 24, 2016 at 19:48

Jinjubei

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1 Comment

Meir Over a year ago

I like this way, but you too, using @ and without it, it return error.

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