How can PHP beginners ensure that their code is secure and follows best practices when including files?

PHP beginners can ensure their code is secure when including files by using the `require_once` or `include_once` functions instead of `require` or `include` to prevent multiple inclusions of the same file. Additionally, they should always sanitize user input before including files to prevent directory traversal attacks. It's also important to use absolute paths when including files to avoid including files from unexpected locations. 

// Example of including a file securely
$filename = '/path/to/secure/file.php';
if (file_exists($filename)) {
    require_once $filename;
} else {
    echo 'File not found';
}

Keywords

PHP file inclusion security best practices validation

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