php连接不上MySQL问题解决办法

function microtime_float()
{
list($usec, $sec) = explode(" ", microtime());
return ((float)$usec + (float)$sec);
}
 
$time_start = microtime_float();
for ( $i=0; $i<30000; $i++){ 
$dbh=new mysqli("XXX.XXX.XXX.XXX", "wubx", "wubxwubx", "userdb", 3308);
$dbh->close();
}
$time_end= microtime_float();
$time_use= ($time_end - $time_start)/30000;
print "$time_usen";
#php tconn.php
0.00090954260031382

net.ipv4.tcp_max_syn_backlog = 819200
net.core.netdev_max_backlog = 400000
net.core.somaxconn = 4096
net.ipv4.tcp_tw_reuse=1
net.ipv4.tcp_tw_recycle=0
#sysctl -p

<?php
header ( 'http-equiv="Content-Type" content="text/html; charset=utf-8"' );
$DB_host = "localhost"; //数据库主机
$DB_user = "root"; //数据库用户
$DB_psw = "root3306"; //数据库密码
$DB_datebase = "gk_yue39_com"; //数据库名
$DB_charset = "utf8"; //数据库字符集
$dbprefix="yue392_com_";
$new_dbprefix="yue39_com_";
$db = new mysqli ( $DB_host, $DB_user, $DB_psw ); //实例化对象

//检查连接
if (mysqli_connect_errno ()) {
 printf ( "Connect failed: %sn", mysqli_connect_error () );
 exit ();
}

$db->select_db ( $DB_datebase ); //选择操作数据库

$db->set_charset ( $DB_charset ); //设置数据库字符集

//执行一个查询
$sql = 'show tables';
$result = $db->query ( $sql );

echo $result->num_rows . ' 行结果  ' . $result->field_count . ' 列内容<br/>';

//$result->data_seek('5');//从结果集中第5条开始取结果

echo '<table border="1" cellspacing="0" cellpadding="0" align="center" width="90%">';

//循环输出字段名
//$result->field_seek(2);//从字段集中第2条开始取结果
while ( true == ($field = $result->fetch_field ()) ) {
 echo '<th>' . $result->current_field . '_' . $field->name . '(' . $field->length . ')</th>';
}

//循环输出查询结果
while ( true == ($row = $result->fetch_assoc ()) ) {
 echo '<tr>';
 foreach ( $row as $col ) {
$sql="rename table `".$col."` to `".str_replace ( $dbprefix, $new_dbprefix, $col)."`";
    if($db->query ( $sql )){
  echo '<td align="center">' . $sql. '</td><td><font color="blue"> success</font></td>';
  }else{
  echo '<td align="center">' . $sql. '</td><td><font color="red"> failed</font></td>';
  } 
  }
 echo '</tr>';
}

echo '</table>';
$result->free ();//释放结果集
$db->close (); //关闭连接
?>

public static function stringFromColumnIndex($pColumnIndex = 0)
    {
        //  Using a lookup cache adds a slight memory overhead, but boosts speed
        //  caching using a static within the method is faster than a class static,
        //      though it's additional memory overhead
        static $_indexCache = array();
 
        if (!isset($_indexCache[$pColumnIndex])) {
            // Determine column string
            if ($pColumnIndex < 26) {
                $_indexCache[$pColumnIndex] = chr(65 + $pColumnIndex);
            } elseif ($pColumnIndex < 702) {
                $_indexCache[$pColumnIndex] = chr(64 + ($pColumnIndex / 26)) .
                                              chr(65 + $pColumnIndex % 26);
            } else {
                $_indexCache[$pColumnIndex] = chr(64 + (($pColumnIndex - 26) / 676)) .
                                              chr(65 + ((($pColumnIndex - 26) % 676) / 26)) .
                                              chr(65 + $pColumnIndex % 26);
            }
        }
        return $_indexCache[$pColumnIndex];
    }

PHPExcel_Cell::stringFromColumnIndex($i); // 从o开始

PHPExcel_Cell::columnIndexFromString(‘AA’);

<?php
/** 备份数据库 生成.sql文件
     * @param $browseinfo  String  浏览器版本
     * return $browseinfo
     */
    function createsql(){
        //创建个日期
        $timer1 = time();
        $path = "my_sql/";
        $content =gettables();
        $filename = $path.$timer1.".sql";
  
        //先判断文件夹在不在
         if(!file_exists($path)){
        //如果不存在生成这个目录,0777表示最大的读写权限
            if(mkdir($path,0777)){
            //echo"新建立目录"; 
            }
        }

        //判断文件是否存在
        if(!file_exists($filename)){
            //如果文件不存在,则创建文件
            @fopen($filename,"w");

            //判断文件是否可写
            if(is_writable($filename)){
            //打开文件以添加方式即"a"方式打开文件流
                if(!$handle =  fopen($filename,"a")){
                    echo"文件不可打开";
                    exit();
                }

            if(!fwrite($handle,$content)){
                echo"文件不可写";
                exit();
            }

        //关闭文件流
        fclose($handle);
        echo "生成文件并保存首次内容";
       
    }else {
        echo"文件$filename不可写";
    }
        }else{
            if(is_writable($filename)){
            //以添加方式打开文件流
            if(!$handle = fopen($filename,"a")){
                echo"文件不可打开";
                exit();
            }
            fclose($handle);
            }else{
                echo "文件$filename不可写";
            }
    }
}

    /**
     * 获得数据库中的表名
     * return $str 循环生成数据库建表和插入值的sql语句
     */
    function gettables(){
        $mysqli = new mysqli("localhost","root","","bbs");
        $str = '';
        if ($result = $mysqli->query("SHOW TABLES")) {
            while($row = $result->fetch_row()){
                $str.= data2sql($row[0])."<br/>";
            }
            $mysqli->close();
            return $str;
        }  
   
    }
   

    /**
     * 获得数据库中的表结构和值
     * return $tabledump 返回一个表中的结构和值的sql语句
     */
    function data2sql($table){ 
     $mysqli = new mysqli("localhost","root","","bbs");
        /* check connection */
        if (mysqli_connect_errno()) {
            printf("Connect failed: %sn", mysqli_connect_error());
        exit();
    }
         $tabledump = "DROP TABLE IF EXISTS $table;n";
         $result = $mysqli->query("SHOW CREATE TABLE $table");
         $create = $result->fetch_row();
         $tabledump .= $create[1].";nn";
 
         $rows = $mysqli->query("SELECT * FROM $table");
         $numfields = $rows->num_rows;

            while ($row = $rows->fetch_row()){
             $comma = "";
             $tabledump .= "INSERT INTO $table VALUES(";
              for($i = 0; $i < $numfields; $i++)
              {
                 $tabledump .= $comma."'".mysql_escape_strin
g($row[$i])."'";
                 $comma = ",";
              }
             $tabledump .= ");n";
          }
         $tabledump .= "n";
 
          return $tabledump;
      }
?>

  select * from tablename order by rand() limit 1 

$query= "SELECT count(*) as count FROM recommends";
....
$max_num = $row['count']; // 取记录总数
srand((double)microtime()*1000000); // 随机数种子
$se_pos = rand(0, $max_num); // 随机数范围
$length = 6; // 记录条数
if (($max_num - $se_pos) <= $length) {
    $se_pos = $max_num - $se_pos; // 记录数不足6条的情况
}

$query = "SELECT * FROM recommendsn limit ".$se_pos.",".$length;

<?php

$db = mysql_connect("localhost", "root");

mysql_select_db("xyj",$db);

$result=mysql_query("SELECT * FROM obj",$db);

$max_num=mysql_num_rows($result);//取得数据库的记录数

srand((double)microtime()*10000000); //生成随机数种子。

$se_pos=rand(0, $max_num-1); //从0到最大记录数取随机数

$length=30; //设定共取多少条记录

//下面是取出指定数目的记录。

$result_lim=mysql_query("select * from obj limit $se_pos,$length",$db);

$myrow_lim=mysql_fetch_array($result_lim);

printf("%sn", $se_pos);//显示随机得到的记录号

printf("%sn", $myrow_lim["name"]);//显示随机得到的记录的name字段