Php if($var) used to work

Question

I have som code for a website, that used to work fine with. I want to check if a variable or session is set. I used the following code:

if ($_GET['something']){ //Do something }

Now i try to install it on a local server, at i get a error code, saying that there is an undefined index.

It requires me to do:

if (isset($_GET['']) { //Do something }

Can i make a quick fix for this, as i don't want to change the code so many places?

Answer 1

You didn't get the error before, because your error_reporting and/or display_error settings were set too forgiving. Your first snippet is attempting to access a value in an array that might not exist. If it doesn't PHP always issues a notice.
It's only after the notice has been issued that it can be hushed up (by turning off display_errors or setting error_reporting to not report notices (~E_NOTICE).

You're asking for a quick fix:

if (isset($_GET['something']))

only requires you to add isset(). That's quick, and it fixes the issue. Besides: using isset is what you should do. Always.

---

Off-topic, but perhaps useful:
As I've explained in the comments: the best course of action for you now is to fix the issue itself, not ignoring the notices. To that end, a simple script that scans your projects directories for .php files (using glob), reads them in and looks for a pattern might prove useful:

foreach ($phpFiles as $file)
{
    $code = file_get_contents($file);//read the file
    if (preg_match_all('/if\s*\(\$[^[]+\[[^]]+\]\s*\)/',$code, $matches))
    {//find all usages of "if ($rawVar['offset'])" in code
        echo 'Expressions to check or fix in file: ', $file,':', PHP_EOL, '=>';
        echo implode(PHP_EOL.'=>', $matches[0]), PHP_EOL;
    }
}

run the script, perhaps write the output to a temp file, and set to work. The output should look something like:

Expressions to check or fix in file: scriptname.php:
=> if ($_GET['something'])
=> if ($var[123])

And so on. It's a workable format, and given time, you might be able to write a script for you to automatically refactor the code, too.
Perhaps a more comprehensive (as in complete) regex to use here would be something like:

/if\s*\((\|\||&&|\()?\$[^[]+\[[^]]+\]\s*(\|\||&&|\))?/

But this, too, has some caveats still, but it's a start.

---

Adding assignments - I'll do you one more favour: adding code that fixes the issues you get in assignment expressions like $var = $_GET['something'];. This can be done automatically, and quite easily, too:

foreach ($phpFiles as $file)
{
    $code = file_get_contents($file);//read the file
    $clean = preg_replace(
        '/(\$[^\s]+\s*={1}\s*)(\$[^[]+[^]]+\])\s*;/',
        '$1isset($2) ? $2 : null;',
        $code
    );
    file_put_contents($file, $clean);
}

I've tested this code like so:

$code = '$foo = 123;
$foo = $_GET["bar"];';
$clean = preg_replace(
    '/(\$[^\s]+\s*={1}\s*)(\$[^[]+[^]]+\])\s*;/',
    '$1isset($2) ? $2 : null;',
    $code
);
echo $clean, PHP_EOL;

And it yielded the expected output:

$foo = 123;
$foo = isset($_GET["bar"]) ? $_GET["bar"] : null;

Combine these two regex's and you should be well on your way to refactoring the code you have...