<?php
class DB_MySQL
 {
/*
加载数据库配置
1 服务器地址 2用户名 3密码 4库名
*/
 public function __construct($servername,$dbusername,$dbpassword,$dbname)
  {
  $this->mysqli = new mysqli($servername, $dbusername, $dbpassword, $dbname);
  if ( mysqli_connect_errno() ) die(mysqli_connect_error());
  }

 public function query($sql)
  {return $this->mysqli->query($sql);}
/*取出刚存入的ID 返回id值 该表必须id自动递增的格式*/
 public function insert_id()
  {return $this->mysqli->insert_id;}

 public function affected_rows($sql)
  {
  $this->query($sql);
  return $this->mysqli->affected_rows;
  }
/*
mysqli_fetch_array返回循环数组方式  mysqli_fetch_array()这个函数需要内容才能输出，如果sql语句出错了，就没有内容了，就警告了
*/
 public function fetch_array($query)
  {return mysqli_fetch_array($query);}
/*单数据sql*/
 public function fetch_one_array($query)
  {return $this->fetch_array($this->query($query));}
/*统计 返回数字*/
 public function fetch_one($query)
  {
  $record = $this->fetch_one_array($query);
  Return $record[0];
  }
/*清除 退出数据连接*/
 public function close()
  {return $this->mysqli->close();}
/*新增字段数字转换*/
 private function compile_db_insert_string($data)
  {
  $field_names = "";
  $field_values = "";
  foreach ($data as $k => $v)
   {
   $field_names .= "$k,";
   $field_values .= "'$v',";
   }
  $field_names = preg_replace( "/,$/" , "" , $field_names );
  $field_values = preg_replace( "/,$/" , "" , $field_values );
  return array('FIELD_NAMES' => $field_names, 'FIELD_VALUES' => $field_values);
  }
/*修改字段数字转换*/
 private function compile_db_update_string($data)
  {
  $return_string = "";
  foreach ($data as $k => $v)
   {
   if(is_array($v))
    {$return_string .= $k . "=".$v['0'].",";}
   else
    {$return_string .= $k . "='".$v."',";}
   }
  return preg_replace( "/,$/" , "" , $return_string );
  }
/*新增*/
 public function insert_sql( $tbl , $arr ,$action="INSERT")
  {
  $dba = $this->compile_db_insert_string( $arr );
  $sql = "{$action} INTO {$tbl} ({$dba['FIELD_NAMES']}) VALUES ({$dba['FIELD_VALUES']})";
  return $sql;
  }
/*修改*/
 public function update_sql($tbl,$arr,$where='')
  {
  $dba = $this->compile_db_update_string( $arr );
  $query = "UPDATE {$tbl} SET $dba";
  if ( $where ) $query .= " WHERE ".$where;
  return $query;
  }
 }
?>