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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. } }