What is the scope of error_get_last() in PHP?

I've been using error_get_last() in combination with register_shutdown_function() to create an error report for some of my scripts. It's been working fine for the most part. Every now and then, though, the error report will show an error from a different script.

I'm not quite sure how that can happen. Can anyone explain? I'm wondering if error_get_last() in one script should be able to show errors from different scripts and if that's the case, under what circumstances would that happen? My only guess is that the error is saved for a short time so that a script that finishes execution at almost the same time might catch another script's errors. Could that be it?

This is the code I use and have included in many different PHP files:

function send_error_report($extra) {
        global $conn;
        $base_url = ( isset($_SERVER['HTTPS']) && $_SERVER['HTTPS']=='on' ? 'https' : 'http' ) . '://' .  $_SERVER['HTTP_HOST'];
        $url = $base_url . $_SERVER["REQUEST_URI"];
        
        $error = error_get_last();
        
        if (isset($error)) {
            $error_str = "Type: " . $error['type'] . " | Message: " . $error['message'] . " | File: " . $error['file'] . " | Line: " . $error['line'];
            $sql = "INSERT INTO `error_report` (`script`, `error`) VALUES ('$url', '" . $error_str . " - " . $extra . "');";
            
            $conn->query($sql);
        }
    }
    register_shutdown_function('send_error_report', '');