原生mysql查询,选择数据库,建立连接及查询数据表PHP完整流程

用mysqli_connect,mysql_connect,mysqli_select_db,mysql_select_db
,mysqli_query,mysql_query直接选择数据库.数据表并进行查询完整代码

database.php文件为数据库的用户或密码等

<?php

return array (
    "default" => array (
        "hostname" => "127.0.0.1",
        "database" => "phpcms",
        "username" => "root",
        "password" => "root",
        "tablepre" => "v9_",
        "charset" => "utf8",
        "type" => "mysql",
        "debug" => true,
        "pconnect" => 0,
        "autoconnect" => 0
        ),
);

?>

$mysql_user=include(PHPS_PATH."/caches/configs/database.php");//得到数据库配置
        $username=$mysql_user["default"]["username"];
        $password=$mysql_user["default"]["password"];
        $tablepre=$mysql_user["default"]["tablepre"];
        $database=$mysql_user["default"]["database"];

        $con = mysqli_connect($mysql_user["default"]["hostname"],$username,$password);//句柄

mysqli_select_db($con,$database);//选择数据库 
$sql = " SELECT * FROM ".$tablepre."pay_account where trade_sn="".$out_trade_no.""";
//file_put_contents("3.txt",$sql);
$result2=mysqli_query($con,$sql);
$orderinfo=mysqli_fetch_array($result2);;
$uid=$orderinfo["userid"];
//更新数据库
$sql4 = " update  ".$tablepre."pay_account set status= "succ"  where userid=".$uid ." and trade_sn="".$out_trade_no.""";
        $result4=mysqli_query($con,$sql4);
                 mysqli_close($con);