I'm running a PHP script and continue to receive errors like:
Notice: Undefined variable: my_variable_name in C:wampwwwmypathindex.php on line 10
Notice: Undefined index: my_index C:wampwwwmypathindex.php on line 11
Line 10 and 11 looks like this:
echo "My variable value is: " . $my_variable_name; echo "My index value is: " . $my_array["my_index"];
What is the meaning of these error messages?
Why do they appear all of a sudden? I used to use this script for years and I've never had any problem.
How do I fix them?
This is a General Reference question for people to link to as duplicate, instead of having to explain the issue over and over again. I feel this is necessary because most real-world answers on this issue are very specific.
Related Meta discussion:
- What can be done about repetitive questions?
- Do “reference questions” make sense?
Notice: Undefined variable
From the vast wisdom of the PHP Manual:
From PHP documentation:
This means that you could use only
empty()to determine if the variable is set, and in addition it checks the variable against the following,
Test the above snippet in the 3v4l.org online PHP editor
Although PHP does not require a variable declaration, it does recommend it in order to avoid some security vulnerabilities or bugs where one would forget to give a value to a variable that will be used later in the script. What PHP does in the case of undeclared variables is issue a very low level error,
E_NOTICE, one that is not even reported by default, but the Manual advises to allow during development.
Ways to deal with the issue:
Recommended: Declare your variables, for example when you try to append a string to an undefined variable. Or use
!empty()to check if they are declared before referencing them, as in:
This has become much cleaner as of PHP 7.0, now you can use the null coalesce operator:
Set a custom error handler for E_NOTICE and redirect the messages away from the standard output (maybe to a log file):
Disable E_NOTICE from reporting. A quick way to exclude just
Suppress the error with the @ operator.
Note: It's strongly recommended to implement just point 1.
Notice: Undefined index / Undefined offset
This notice appears when you (or PHP) try to access an undefined index of an array.
Ways to deal with the issue:
Check if the index exists before you access it. For this you can use
The language construct
list()may generate this when it attempts to access an array index that does not exist:
Two variables are used to access two array elements, however there is only one array element, index
0, so this will generate:
The notices above appear often when working with
$_GETyou just have to check if the index exists or not before you use them. For
$_SESSIONyou have to make sure you have the session started with
session_start()and that the index also exists.
Also note that all 3 variables are superglobals and are uppercase.