ช่วยทีครับ Fatal error: Uncaught Error: Call to undefined function mysql_connect()

<?php
	session_start();
	$serverName = "127.0.0.1";
	$dbName = "ttt";

	$objCon = mysqli_connect($serverName,$dbName);

	$strSQL = "SELECT * FROM member WHERE Username = '".mysqli_real_escape_string($objCon,$_POST['txtUsername'])."' 
	and Password = '".mysqli_real_escape_string($objCon,$_POST['txtPassword'])."'";
	$objQuery = mysqli_query($objCon,$strSQL);
	$objResult = mysqli_fetch_array($objQuery,MYSQLI_ASSOC);
	if(!$objResult)
	{
			echo "Username and Password Incorrect!";
	}
	else
	{
			$_SESSION["UserID"] = $objResult["UserID"];
			$_SESSION["Status"] = $objResult["Status"];

			session_write_close();
			
			if($objResult["Status"] == "ADMIN")
			{
				header("location:admin_page.php");
			}
			else
			{
				header("location:user_page.php");
			}
	}
	mysqli_close($objCon);
?>