删除未定义的索引[重复]

Question

This question already has an answer here:

• “Notice: Undefined variable”, “Notice: Undefined index”, and “Notice: Undefined offset” using PHP 28 answers

None of the solutions in the other threads were clear. I need help removed the undefined message. The line of code that is causing it is this variable:

$ain = $_Get['AIN'];

Other threads mentioned using upset although I could not follow. I want to be able to pass a value in whether it is null or not.

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Answer 1

You have to check the existence of the array index before using it, and provide an alternative value to use in case it isn't set.

For example:

if(isset($_GET['AIN'])){
  //The value is set and you can use it
  $ain = $_GET['AIN'];
} else {
  //The value is not set, so you should provide a default value
  $ain = NULL;
}

Also note that the PHP language is case sensitive, so if you want to refer to HTTP GET parameters, you should use $_GET, because $_Get will not work.