How can including files multiple times in PHP cause errors, and how can it be avoided?

Including files multiple times in PHP can cause errors such as redeclaration of functions or classes, which can lead to fatal errors. To avoid this issue, you can use conditional statements to check if the file has already been included before including it again. 

// Check if the file has already been included before including it
if (!defined('INCLUDED_FILE')) {
    define('INCLUDED_FILE', true);
    include 'your_file.php';
}

Keywords

PHP include_once require_once file inclusion error handling

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