Possible Duplicate: PHP: “Notice: Undefined variable” và “Notice: Undefined index”

Good day!

I am having the following error in my code:

add Employee " method="POST">

SSN

How can I remove the error above? Thank you.

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It should be a notice & not an error.

To fix is you"ll have to kiểm tra whether $_POST<"submit"> is set:

if(!isset($_POST<"submit">)) ...

It"s where you chạy thử to see that is isn"t there. It should be !isset($_POST<"SUBMIT">). This is because the index, SUBMIT, won"t be set, thus won"t have a value such as true lớn pass the if(...). Isset() checks lớn see if the index/variable is actually set.

Try this:

Add Employee" method="POST">

SSN

sign in front of the variable name, which will suppress the error on that particular line.Change your code to use isset($_POST<"SUBMIT">) before checking it further.

Of these, the third option is definitely the best. You shouldn"t assume that any variable supplied by the user will be mix as you expect; you should always check that it"s set at all, and also that it"s set lớn the expected values. Otherwise you are liable to lớn be mở cửa to hacking attacks.

"Notice: Undefined variable", "Notice: Undefined index", "Warning: Undefined array key", & "Notice: Undefined offset" using PHP
"Notice: Undefined variable", "Notice: Undefined index", "Warning: Undefined array key", and "Notice: Undefined offset" using PHP
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PHP is a widely used scripting language that is mainly used for website development purposes. It is a scripting language và finds application in automating tasks that would otherwise be impossible lớn implement with just human intervention. Being a server-side language, it primarily takes care of things at the server’s end. Launched in 1995 for public use, it has remained a popular choice among web developers since then.

Programming is a tricky business. It is pretty normal lớn stumble upon errors and warnings while making a program. The same happens a lot to PHP developers, like when they face an Undefined index in PHP. However, such errors are not hard to deal with with a little bit of knowledge & guidance.

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What Is an Undefined Index PHP Error?

Websites often use forms to lớn collect data from visitors. PHP uses $GET và $POST methods for such data collection. This data is collected & saved in variables that are used by the website to lớn work và serve the visitor further. Many a time, some fields are left blank by the user. But the website tries to refer khổng lồ these fields for proceeding further. That means the PHP code tries to lớn get the value of the field that no one has defined and thus does not exist. Quite expectedly, it does not work & raises a notice called Undefined Index in PHP.

Code: 

Grade: ‘.$grade;

?>

Result: 

You can fix it using the isset() function, which we will discuss further in the upcoming sections.

Undefined Index is a notice in PHP, and it is a choice of the developer khổng lồ either ignore it or fix it.

How lớn Ignore PHP Notice: Undefined Index?

Undefined Index in PHP is a Notice generated by the language. The simplest way lớn ignore such a notice is lớn ask PHP to lớn stop generating such notices. You can either địa chỉ a small line of code at the đứng đầu of the PHP page or edit the field error_reporting in the php.ini file.

1. Adding Code at the đứng top of the Page

A simple way to ask PHP to lớn disable reporting of notices is to put a line of code at the beginning of the PHP page.

Code:

 

Or you can địa chỉ cửa hàng the following code which stops all the error reporting,

 

2. Changes in php.ini 

Php.ini is a configuration file and is essential for all the programs running on PHP. Mở cửa this file và find the field error_reporting. The easiest way is to use the ctrl + F shortcut key. By default, error reporting is set to lớn E_ALL. That means all errors are reported. Change this to E_ALL và ~E_NOTICE. It means all errors except for the notices will now be reported.

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How khổng lồ Fix the PHP Notice: Undefined Index?

We know the cause of the error. It occurs when we use $_GET and $_POST methods lớn get input, but we reference it even when it has not been set. The solution simply is to kiểm tra if it has been mix before referencing.

We can use the isset() function, which checks if the variable ‘is set’ or not before referencing khổng lồ them. Isset() function returns True or False depending on it.

Undefined Index in PHP $_GET

When using the $_GET method, the following code might show the notice Undefined index in PHP:

Code:

Age: '.$age;

echo 'Grade: '.$grade;

?>

As we have not set any of these variables, this code shows the Undefined Index notice.

Change it khổng lồ the following code lớn fix this issue:

Code:

Age: '.$age;

echo 'Grade: '.$grade;

?>

Result: 

We can use a single line of code lượt thích this instead.

Code:

This approach also achieves the intended goal.

Result:

Notice: Undefined Variable

PHP shows this notice when we try to use a variable even before defining it.

Code:

Result:

It can be solved either by declaring a variable global and then using isset() khổng lồ see if it is phối or not. It can be echoed only if it has been set. Alternatively, we can use isset(X) ? Y to set a default.

Code:

Result: 

We can set it after the isset() kiểm tra like this.

Code: 

Result:

Notice: Undefined Offset

It shows Undefined Offset Notice in PHP when we are referring to lớn a key in an array that has not been phối for the array.

Here’s an example.

Code:

'one', 2=>'two', 4=>'four');

echo $name
Array<3>;

?>

Result:

It might show an undefined array key warning for some. It means the same thing that you are trying khổng lồ access an undefined array key.

It can be solved similarly lượt thích the last two cases by using isset(), arrayexists() or empty() function.

Code: 

'one', 2=>'two', 4=>'four');

echo 'using isset()';

echo 'key 3 ';

if(isset($name
Array<3>))

echo $name
Array<3>;

echo 'key 1 ';

if(isset($name
Array<1>))

echo $name
Array<1>;

echo ' using array_key_exists ';

echo 'key 3 ';

echo array_key_exists(3, $name
Array);

echo ' key 2 ';

echo array_key_exists(2, $name
Array);

echo 'using empty ';

echo 'key 3 ';

if(!empty($name
Array<3>))

echo $name
Array<3>;

echo 'using key 4 ';

if(!empty($name
Array<4>))

echo $name
Array<4>;

?>

Result:

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Conclusion

In this article, we learned about the undefined index in PHP. However, it is just one of the many errors, warnings, và notices that a PHP developer has to giảm giá khuyến mãi with. If you are looking lớn make a career out of developing web applications và handling such errors, cachseo.com is offering a Post Graduate Program in Full stack web Development, in partnership with Caltech CTME. cachseo.com is the world’s #1 online Bootcamp that has helped advance 2,000,000 careers through collaboration with World’s top-ranking universities.