What are the security implications of using PHP scripts that rely on register globals being turned on?

When using PHP scripts that rely on register globals being turned on, there is a significant security risk as it can lead to vulnerabilities such as injection attacks and data manipulation. It is recommended to rewrite the scripts to use superglobals like $_GET, $_POST, and $_REQUEST instead.

// Example of how to rewrite a script to use superglobals instead of relying on register globals
$myVar = isset($_GET['myVar']) ? $_GET['myVar'] : '';