Deprecated: mysql_connect(): The mysql extension is deprecated and will be removed in the future: use mysqli or PDO instead in /home/iewfm/public_html/research/include/dbconnection.php on line 9

php error happened

	Technical information
Error type	2
Error description	Cannot modify header information - headers already sent by (output started at /home/iewfm/public_html/research/include/dbconnection.php:9)
URL	iewfm.starhostbd.com/research/research_list.php?
Error file	/home/iewfm/public_html/research/include/commonfunctions.php
Error line	3909
SQL query

Call stack
	File: line	Function	Arguments
#0.	include/commonfunctions.php:3909	header	1. Cache-Control: no-cache, no-store, max-age=0, must-revalidate;
#1.	include/commonfunctions.php:3909	add_nocache_headers	N/A
#2.	research_list.php:7	Global scope	N/A