求助！！！！！我都要崩溃了 ！！！！

<?php
$server="127.0.0.1";
$username="root";
$password="123456";
$database="zichao";
$conn=mysqli_connect($server,$username,$password)
or die("could not connect mysql");
mysqli_select_db($conn,$database)
or die("could not open database");
?>

mysql_select_db和mysqli_select_db的两个参数顺序正好相反

$conn=new mysqli('你的url','用户名','密码','数据库');
if(mysqli_connect_errno()===0){
echo 'ok!';
}else{
die(mysqli_connect_error());
}
$conn->query("SET NAMES 'utf8'");
$conn->close();
------------------------------------------------------------------------------
-----------------面向过程不推荐---------------------------
$conn=mysqli_connect('url','dbuser','dbpwd','dbname');
if(mysqli_connect_errno()!==0){
die(mysqli_connect_error());
}
mysqli_query($conn,"SET NAMES 'utf8'");
mysqli_close($conn);

$conn=new mysqli('你的url','用户名','密码','数据库');//这个我不说了!
if(mysqli_connect_errno()===0){//如果等于0证明没有问题
echo 'ok!';
}else{
die(mysqli_connect_error());//输出失败原因;
}
$conn->query("SET NAMES 'utf8'");//防止乱码;
$conn->close();//关闭;
------------------------------------------------------------------------------
-----------------面向过程不推荐---------------------------
$conn=mysqli_connect('url','dbuser','dbpwd','dbname');
if(mysqli_connect_errno()!==0){
die(mysqli_connect_error());
}
mysqli_query($conn,"SET NAMES 'utf8'");
mysqli_close($conn);