PHP+MySQL选择数据库

<?php
$host = "127.0.0.1";
$userName = "root";
$password = "root";
$dbName = "db_database13";
$connID = mysql_connect($host, $userName, $password);
if(mysql_select_db($dbName, $connID)){
echo "数据库选择";
}else{
echo "数据库选择失败";
}
?>