How can the use of extract() function in PHP be risky when dealing with form data?

Using the extract() function in PHP when dealing with form data can be risky because it can extract all variables from the form data into the current symbol table, potentially overwriting existing variables or introducing unexpected variables into the script. To mitigate this risk, it is recommended to manually retrieve and sanitize form data using $_POST or $_GET superglobals instead of using extract(). 

// Retrieve and sanitize form data using $_POST superglobal
$username = isset($_POST['username']) ? htmlspecialchars($_POST['username']) : '';
$password = isset($_POST['password']) ? htmlspecialchars($_POST['password']) : '';
$email = isset($_POST['email']) ? filter_var($_POST['email'], FILTER_SANITIZE_EMAIL) : '';

Keywords

extract function PHP form data security

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