What to do if php undefined variable error occurs

Solutions to PHP undefined variable errors: 1. Initialize the variable for assignment; 2. Add the @ symbol to suppress the error, code such as "$sid = @$_POST['sid'];".

The operating environment of this article: Windows 7 system, PHP version 7.1, DELL G3 computer

What should I do if I get an undefined variable error in php?

PHP Solving undefined variable errors

Sometimes this error

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

will appear in PHP. The reason is that it is not defined, because PHP is Weakly typed languages, unlike JAVA, do 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 1: Initialization Assigning values ​​to variables

Method 2: Add @ to suppress errors

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

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