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There are two methods in PHP called $_POST and $_GET methods which are used to obtain the input from the user while using a form and while using them. if there is any variable or constant with no values assigned to them, then an error is encountered called undefined index in the form “Notice: Undefined index” and this undefined index error can be of the following forms namely “Notice: Undefined variable”, “Notice: Undefined index” and “Notice: Undefined offset” and such errors can be handled in two ways either by resolving such notices or by ignoring such notices and to resolve such notice, we make use of a function called isset() function in PHP and to ignore such notices, we update the option error_reporting to ~E_NOTICE to disable the notice reporting.
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To declare undefined index in PHP is as follows:
Notice: Undefined index:/Undefined variable:/Undefined offset
Working of the undefined index in PHP is as follows:
Following are the examples are given below:
PHP program to illustrate the undefined index error in which we are supposed to provide the two inputs and not giving them causes undefined index error:
Code:
<html> <body> <?php #a variable called country is defined to store the input from the user through $_GET method $country = $_GET['country']; #a variable called capital is defined to store the input from the user through $_GET method $capital = $_GET['capital']; #displaying the input obtained by the user otherwise undefined index error is encountered echo $country; echo $capital; ?> </body> </html>
Output:
In the above program, a variable called country is defined to store the input provided by the user through $_GET method. Then another variable called capital is defined to store the input provided by the user though $_GET method. Then the input provided by the user is displayed on the screen. In case no input is provided by the user undefined index error is encountered as shown in the output. The output is shown in the snapshot above.
PHP program to illustrate the undefined index error in which we are supposed to provide the two inputs and not giving them causes undefined index error:
Code:
<html> <body> <?php #a variable called model is defined to store the input from the user through $_GET method $model = $_GET['car_model']; #a variable called yearl is defined to store the input from the user through $_GET method $year = $_GET['year_of_purchase']; #displaying the input obtained by the user otherwise undefined index error is encountered echo $model; echo $year; ?> </body> </html>
Output:
In the above program, a variable called model is defined to store the input provided by the user through $_GET method. Then another variable called year is defined to store the input provided by the user though $_GET method. Then the input provided by the user is displayed on the screen. In case no input is provided by the user undefined index error is encountered as shown in the output. The output is shown in the snapshot above.
PHP program to illustrate the undefined index error in which we are supposed to provide the two inputs and not giving them causes undefined index error:
Code:
<html> <body> <?php #a variable called source is defined to store the input from the user through $_GET method $source = $_GET['source']; #a variable called destination is defined to store the input from the user through $_GET method $destination = $_GET['destination']; #displaying the input obtained by the user otherwise undefined index error is encountered echo $source; echo $destination; ?> </body> </html>
Output:
In the above program, a variable called source is defined to store the input provided by the user through $_GET method. Then another variable called destination is defined to store the input provided by the user though $_GET method. Then the input provided by the user is displayed on the screen. In case no input is provided by the user undefined index error is encountered as shown in the output. The output is shown in the snapshot above.
Some of the advantages are as follows:
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