Notice undefined index name in php

[Solved] Notice: Undefined index error in PHP

When working with arrays in PHP, you are likely to encounter «Notice: Undefined index» errors from time to time.

In this article, we look into what these errors are, why they happen, the scenarios in which they mostly happen, and how to fix them.

Let’s first look at some examples below.

Examples with no errors

Example 1

 "John", "last_name" => "Doe"); echo "The first name is ".$person["first_name"]; echo "
"; echo "The last name is ".$person["last_name"]; 

The first name is John
The last name is Doe

Example 2

"; echo $students[0]."
"; echo $students[1]."
"; echo $students[2]."
"; echo $students[3]; 

Our 4 students include:
Peter
Mary
Niklaus
Amina

Examples with errors

Example 1

 "John", "last_name" => "Doe"); echo $employee["age"]; 

Notice: Undefined index: age in /path/to/file/filename.php on line 3

Example 2

Notice: Undefined offset: 3 in /path/to/file/filename.php on line 3

Let’s now examine why the first two examples worked well without errors while the last two gave the «Undefined index» error.

The reason why the last examples give an error is that we are attempting to access indices/elements within an array that are not defined (set). This raises a notice.

For instance, in our $employee array, we have only defined the «first_name» element whose value is «John«, and «last_name» element with value «Doe» but trying to access an element «age» that has not been set in the array.

In our other example with the error, we have created an indexed array namely $devs with 3 elements in it. For this type of array, we use indices to access its elements. These indices start from zero [0], so in this case, Mary has index 0, Niklaus has index 1, and Rancho index 2. But we tried to access/print index 3 which does not exist (is not defined) in the array.

On the other hand, you will notice that in our first two examples that had no errors, we only accessed array elements (either through their keys or indices) that existed in the array.

The Solutions

1. Access only the array elements that are defined

Since the error is caused by attempting to access or use array elements that are not defined/set in the array, the solution is to review your code and ensure you only use elements that exist in the array.

If you are not sure which elements are in the array, you can print them using the var_dump() or print_r() functions.

Example

 "John", "last_name" => "Doe", "email" => "johndoe@gmail.com"); var_dump($user); //Example 2 $cars = array("Toyota","Tesla","Nisan","Bently","Mazda","Audi"); print_r($cars); 

array(3) < ["first_name"]=>string(4) «John» [«last_name»]=> string(3) «Doe» [«email»]=> string(17) «johndoe@gmail.com» >

Array ( [0] => Toyota [1] => Tesla [2] => Nisan [3] => Bently [4] => Mazda [5] => Audi )

This way, you will be able to know exactly which elements are defined in the array and only use them.

In the case of indexed arrays, you can know which array elements exist even without having to print the array. All you need to do is know the array size. Since the array indices start at zero (0) the last element of the array will have an index of the array size subtract 1.

To get the size of an array in PHP, you use either the count() or sizeof() functions.

Example

Note: Though the size of the array is 6, the index of the last element in the array is 5 and not 6. The indices in this array include 0, 1, 2, 3, 4, and 5 which makes a total of 6.

If an element does not exist in the array but you still want to use it, then you should first add it to the array before trying to use it.

2. Use the isset() php function for validation

If you are not sure whether an element exists in the array but you want to use it, you can first validate it using the in-built PHP isset() function to check whether it exists. This way, you will be sure whether it exists, and only use it then.

The isset() returns true if the element exists and false if otherwise.

Example 1

 "John", "last_name" => "Doe"); if(isset($employee["first_name"])) < echo "First name is ".$employee["first_name"]; >if(isset($employee["age"]))

Though no element exists with a key «age» in the array, this time the notice error never occurred. This is because we set a condition to use (print) it only if it exists. Since the isset() function found it doesn’t exist, then we never attempted to use it.

Scenarios where this error mostly occur

The «Notice: Undefined index» is known to occur mostly when using the GET and POST requests.

The GET Request

Let’s say you have a file with this URL: https://www.example.com/register.php.

Some data can be passed over the URL as parameters, which are in turn retrieved and used in the register.php file.

That URL, with parameters, will look like https://www.example.com/register.php?fname=John&lname=Doe&age=30

In the register.php file, we can then collect the passed information as shown below.

We can use the above data in whichever way we want (eg. saving in the database, displaying it on the page, etc) without any error.

But if in the same file we try accessing or using a GET element that is not part of the parameters passed over the URL, let’s say «email», then we will get an error.

Example

Notice: Undefined index: email in /path/to/file/filename.php on line 2

Solution

Note: GET request is an array. The name of the GET array is $_GET . Use the var_dump() or print_r() functions to print the GET array and see all its elements.

Like in our register.php example with URL parameters above, add the line below to your code:

array(3) < ["fname"]=>string(4) «John» [«lname»]=> string(3) «Doe» [«age»]=> string(2) «30» >

Now that you know which elements exist in the $_GET array, only use them in your program.

As in the solutions above, you can use the isset() function just in case the element doesn’t get passed as a URL parameter.

In such a scenario you can first initialize all the variables to some default value such as a blank, then assign them to a real value if they are set. This will prevent the «Undefined index» error from ever happening.

 if(isset($_GET["lname"])) < $lastname = $_GET["lname"]; >if(isset($_GET["email"])) < $email = $_GET["email"]; >if(isset($_GET["age"]))

The POST Request

The POST request is mainly used to retrieve the submitted form data.

If you are experiencing the «Undefined index» error with form submission post requests, the most probable cause is that you are trying to access or use post data that is not being sent by the form.

For instance, trying to use $_POST[«email»] in your PHP script while the form sending the data has no input field with the name «email» will result in this error.

The easiest solution for this is to first print the $_POST array to find out which data is being sent. Then you review your HTML form code to ensure that it contains all the input fields which you would want to access and use in the PHP script. Make sure that the value of the name attributes of the form input matches the array keys you are using in the $_POST[] of your PHP.

In a similar way to the solution we have covered on GET requests on using the isset() function to validate if the array elements are set, do it for POST.

You can in a similar way initialize the values of the variables to a default value (eg. blank), then assign them the real values if they are set.

 if(isset($_GET["lname"])) < $lastname = $_POST["lname"]; >if(isset($_GET["email"])) < $email = $_POST["email"]; >if(isset($_POST["age"]))

If the HTML form and the PHP code processing the file are in the same file, then ensure that the form processing code doesn’t get executed before the form is submitted.

You can achieve this by wrapping all the processing code in a condition that checks if the form has even been sent as below.

That’s all for this article. It’s my hope it has helped you.

Related Articles

Источник

How to solve PHP undefined index notice

Posted on Aug 02, 2022

When accessing an array in PHP, you may see a notice message that says “undefined index” as follows:

When accessing the PHP page from the browser, the following notice message appears:

The Notice: Undefined index message means that the index key you use to access an array’s value doesn’t exist.

In the above example, the array $my_arr only has the name index key. The age index is undefined.

To solve this notice message, you need to make sure that the index is defined inside the array.

The easiest way to do so is by calling the isset() function on the array index before accessing it.

Consider the example below:

 The isset() function in PHP will make sure that the age index is defined in $my_arr .

Combine it with an if condition to create a conditional block that runs when the array index is defined.

Alternatively, you can also use the null coalescing operator to provide a fallback value when the index is undefined like this:

Because the age index is undefined in the example above, the integer 29 is will be printed by the echo function.

The null coalescing operator is useful when you have a fallback value in case the first value is undefined.

Both isset and null coalescing operator also works when you are accessing form values with $_GET and $_POST global variable.

Suppose you’re accessing a PHP page with the following GET parameters:

index.php?name=nathan&age=22

The following code checks if you have a GET parameter named age :

 Or if you want to use the null coalescing operator:

   You can use the same methods with the $_POST variable.

Remove the undefined index notice

While the notice message is useful, you may want to turn it off in production environment so your visitors won’t see it.

When you don’t want the undefined index notice to appear, you can remove it by setting the error_reporting() function at the top of your PHP page.

Now your PHP compiler will not show any notice messages, but other error messages will still be shown.

The error_reporting() function works only for the page where you call the function.

To make it work for all of your PHP pages, you need to set the configuration in your php.ini file as follows:

By setting the configuration in php.ini file, all pages will not show notice messages.

Conclusion

Now you’ve learned what is an undefined index notice in PHP and how to resolve the message.

You can use the isset() function or null coalescing operator to deal with an undefined index in PHP.

You can also remove the notice message by setting the error_reporting parameter in php.ini file, or calling the error_reporting() function.

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