What potential issues can arise from using $_REQUEST to merge arrays in PHP?

Using $_REQUEST to merge arrays in PHP can lead to security vulnerabilities such as injection attacks or unexpected data manipulation. To mitigate these risks, it is recommended to use specific superglobals like $_GET, $_POST, or $_COOKIE based on the intended data source.

// Example of merging arrays using specific superglobals to avoid security risks
$mergedArray = array_merge($_GET, $_POST);