What should I do if PHP warns that the variable is not defined?

php warning variables are not defined because PHP is a weakly typed language, so a warning will appear. The solution is: 1. Check the corresponding PHP code file; 2. Find the variable code, then initialize the variable and assign it. ;3. Add @ to suppress errors, code such as "$sid = @$_POST['sid'];".

The operating environment of this tutorial: windows7 system, PHP version 8.1, DELL G3 computer

What should I do if the php warning variable is not defined? ?

PHP solves the undefined variable error:

Sometimes this error

Notice: Undefined index: sid in D:\Apache Group\Apache2\htdocs\php_mobile\mobile\chao\sinnsei_publish.php on line 10

appears in PHP because it is not defined , because PHP is a weakly typed language, unlike JAVA, etc., it does not necessarily need to be initialized, so this problem is actually not a big problem

However, it does not look good when it appears on the page

Method One: Initialize variables for assignment

Method Two: Add @ to suppress errors

$sid = @$_POST['sid'];

Note: Using @ is a very bad programming habit, because it will not make the error disappear, it just Hiding them, and it makes debugging worse because we can't see what's actually wrong with our code.

Recommended learning: "PHP Video Tutorial"

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