请教数据库连接问题(未定义的功能?)

adillida

全安装redhat linux 8.0,打开了http和mysql服务,用mozilla查看http://localhost/test1.php出错:Fatal error: Call to undefined function: mysql_connect() in /var/www/html/test1.php on line 2.
附录:test1.php:
<?php
$cnn = mysql_connect("localhost","root","");
echo $cnn;
?>