How can the inclusion of external files impact the execution of PHP code?

Including external files in PHP can impact the execution of code by introducing new variables, functions, or classes that may conflict with existing ones. To avoid conflicts, it's important to properly namespace your code or use functions like `require_once` or `include_once` to ensure that external files are only included once. 

// Example of using require_once to include an external file safely
require_once 'external_file.php';
// Your PHP code here

Keywords

file inclusion PHP code execution security vulnerabilities include_once require_once

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