How can including external files impact the availability of variables within PHP functions?

Including external files in PHP can impact the availability of variables within functions if the variables are not properly scoped. To ensure that variables are accessible within functions after including an external file, you can use the `global` keyword to declare the variable as global within the function. 

// external_file.php
$externalVar = "Hello from external file!";

// main_file.php
include 'external_file.php';

function myFunction() {
    global $externalVar;
    echo $externalVar;
}

myFunction(); // Output: Hello from external file!

Keywords

PHP external files variables scope functions

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