Debug_backtrace notice-what’s causing it in my code?

[dwest100]

I have this function which works except it throws a Notice regarding the 3rd line of the function. The Notice reads "Only variables should be passed by reference..." What am I doing wrong in that 3rd line—$caller = next(debug_backtrace()) [‘function’]; ?
Thanks for any assistance!

//EMAIL_ADMIN
//Sends email to site admin if email testing services fail.
//Only occurs if both primary and secondary services have failed.
//Calls no other function.
//Called by test_email function.
//***************************************************************

function email_admin($email){
    global $full_site_url;//used in links.
    global $site_title;//used in confirmation messages.
    $caller = next(debug_backtrace())['function']; //assigns calling function name to $caller.
    
    if ($caller == 'alt_test_email'){
        //used in email message to provide links for checking services.
        $primary_service = 'http://www.quickemailverification.com';//used in email message.
        $secondary_service = 'http://www.neverbounce.com';//used in email message.

        $to = get_bloginfo('admin_email');
        $subject = 'EMAIL TESTING SERVICES HAVE FAILED!';
        $message = 'Both email testing services have failed. Go to ' . $primary_service . ' and ' . $secondary_service . '.';
        dw_send_email($to, $subject, $message);//call email sending function.
    }
    
    if ($caller == 'unsubscribe'){
        $to = get_bloginfo('admin_email');
        $subject = $site_title . " unsubscribe";
        $message = $email . " has unsubscribed.";
        dw_send_email($to, $subject, $message);//call email sending function.
    }
    
    if ($caller == 'subscribe_form_display'){
        $to = get_bloginfo('admin_email');
        $subject = "New " . $site_title . " subscriber";
        $message = $email . " has subscribed to " . $site_title . ".";
        dw_send_email($to, $subject, $message);//call email sending function.
    }
}

 

[requinix]

next() operates on array variables. You are trying to give it an array that is not a variable.

It's trying to get the second item in that backtrace array. Use regular array offset [ ] notation instead - yes, you can do it right after a function call.

[dwest100]

Thanks much! I will do that 🙂

[dwest100]

Got it squared away! Thanks!