What are common causes of "undefined array key" errors in PHP when using AJAX?

Common causes of "undefined array key" errors in PHP when using AJAX include accessing an array key that does not exist in the array being passed from the AJAX request. To solve this issue, you should always check if the array key exists before accessing it to avoid the error. 

// Check if the array key exists before accessing it
if(isset($_POST['key'])) {
    $value = $_POST['key'];
    // Use the value here
} else {
    // Handle the case when the key is not set
}

Keywords

PHP AJAX undefined array key error troubleshooting

Related Questions