PHP5.6连接数据库和一些简单操作

<?php
/**
* Created by PhpStorm.
* User: Administrator
* Date: 2018/1/23
* Time: 13:54
*/

/*
* @method connDb:数据库链接
* @param:null
* @return:$conn
*
* */
function connDb(){

$conn=mysqli_connect('p:localhost','root','','ym');
if (mysqli_connect_errno()){
printf("Connect failed:5s\n",mysqli_connect_error());
exit();
}else{

return $conn;
}

}

/*
* @method updateDb:更新数据库的时间和北方情况
* @param:null
* @return:$flag 成功/失败
*
* */
function updateDb($now,$die_flag,$conn,$host){

$arr = array();

$query="UPDATE domians set die_flag='".$die_flag."', datetime='".$now."' WHERE host='".$host."'";
//$result = mysqli_query($conn,$query);

$result=mysqli_query($conn,$query);

if ($result){

$arr['stat']="suc";

}else{
//echo "更新失败,".$result;
$arr['stat']="fail";
$arr['error']=$result;
}

echo json_encode($arr);
}

/*
* @method selectByOldTime:获取未检测的最老域名
* @param:null
* @return:$conn
*
* */
function selectByOldTime(){

$arr = array();
$conn = connDb();
$sql='select id,host from domians ORDER BY datetime DESC';
//$sql="select * from domians";

$result=mysqli_query($conn,$sql);

if (! $result){

printf("Error:%s\n",mysqli_error($conn));

exit();
}  else{

//$row=mysqli_fetch_array($result,MYSQL_ASSOC);

$row= mysqli_fetch_assoc($result);

mysqli_close($conn);

//echo $row['host'];

$arr['id'] = $row['id'];
$arr['host'] = $row['host'];

echo json_encode($arr);

//return $row['host'];
}
}

function insertDb(){

$mysql_table="domians";

$conn = connDb();

$host="www.baidu.com";

$sql_insert="insert into $mysql_table(host,die_flag,datetime) VALUE ('".$host."',0,'".time()."')";
echo $sql_insert;
if (mysqli_query($conn,$sql_insert)){

echo "插入成功";
}else{
echo "插入失败".mysqli_error($conn);
}

mysqli_close($conn);
}

$value=null;
$getHost=null;
if (isset($_GET["action"])){
$value= $_GET["action"];
}
if (isset($_GET['host'])){
$getHost= $_GET["host"];
}

if ($value!=null){

switch ($value)
{
case "select":

selectByOldTime();
break;

case "updatetime":

if ($getHost==null){

echo "域名未指定";
exit();
}

updateDb(time(),0,$conn,$getHost);

break;

case "updatedie_flag":

if ($getHost==null){

echo "域名未指定";
exit();
}
updateDb(time(),1,$conn,$getHost);

default:
echo "action不存在的，相信我！";
}
}else{
echo "action未指定";
}

/*
while ($row=mysqli_fetch_assoc($result)){
echo $row['id']."______".$row['username'].'<br/>';
}*/