PHP DB 数据库连接类定义与用法示例

<?php
// 数据库连接类
class DB{
 //私有的属性
 private static $dbcon=false;
 private $host;
 private $port;
 private $user;
 private $pass;
 private $db;
 private $charset;
 private $link;
 //私有的构造方法
 private function __construct(){
  $this->host = 'localhost';
  $this->port = '3306';
  $this->user = 'root';
  $this->pass = 'root';
  $this->db = 'imooc';
  $this->charset= 'utf8';
  //连接数据库
  $this->db_connect();
  //选择数据库
  $this->db_usedb();
  //设置字符集
  $this->db_charset();
  }
  //连接数据库
  private function db_connect(){
  $this->link=mysqli_connect($this->host.':'.$this->port,$this->user,$this->pass);
  if(!$this->link){
   echo "数据库连接失败<br>";
   echo "错误编码".mysqli_errno($this->link)."<br>";
   echo "错误信息".mysqli_error($this->link)."<br>";
   exit;
  }
  }
  //设置字符集
  private function db_charset(){
   mysqli_query($this->link,"set names {$this->charset}");
  }
  //选择数据库
  private function db_usedb(){
   mysqli_query($this->link,"use {$this->db}");
  }
  //私有的克隆
  private function __clone(){
   die('clone is not allowed');
  }
  //公用的静态方法
  public static function getIntance(){
   if(self::$dbcon==false){
   self::$dbcon=new self;
   }
   return self::$dbcon;
  }
  //执行sql语句的方法
  public function query($sql){
   $res=mysqli_query($this->link,$sql);
   if(!$res){
   echo "sql语句执行失败<br>";
   echo "错误编码是".mysqli_errno($this->link)."<br>";
   echo "错误信息是".mysqli_error($this->link)."<br>";
   }
   return $res;
  }
  //获得最后一条记录id
  public function getInsertid(){
   return mysqli_insert_id($this->link);
  }
  /**
  * 查询某个字段
  * @param
  * @return string or int
  */
  public function getOne($sql){
   $query=$this->query($sql);
   return mysqli_free_result($query);
  }
  //获取一行记录,return array 一维数组
  public function getRow($sql,$type="assoc"){
   $query=$this->query($sql);
   if(!in_array($type,array("assoc",'array',"row"))){
    die("mysqli_query error");
   }
   $funcname="mysqli_fetch_".$type;
   return $funcname($query);
  }
  //获取一条记录,前置条件通过资源获取一条记录
  public function getFormSource($query,$type="assoc"){
  if(!in_array($type,array("assoc","array","row")))
  {
   die("mysqli_query error");
  }
  $funcname="mysqli_fetch_".$type;
  return $funcname($query);
  }
  //获取多条数据，二维数组
  public function getAll($sql){
   $query=$this->query($sql);
   $list=array();
   while ($r=$this->getFormSource($query)) {
   $list[]=$r;
   }
   return $list;
  }
  public function selectAll($table,$where,$fields='*',$order='',$skip=0,$limit=1000)
  {
       if(is_array($where)){
          foreach ($where as $key => $val) {
            if (is_numeric($val)) {
              $condition = $key.'='.$val;
            }else{
              $condition = $key.'=\"'.$val.'\"';
            }
          }
       } else {
        $condition = $where;
       }
       if (!empty($order)) {
         $order = " order by ".$order;
       }
       $sql = "select $fields from $table where $condition $order limit $skip,$limit";
       $query = $this->query($sql);
       $list = array();
       while ($r= $this->getFormSource($query)) {
         $list[] = $r;
       }
       return $list;
  }
   /**
   * 定义添加数据的方法
   * @param string $table 表名
   * @param string orarray $data [数据]
   * @return int 最新添加的id
   */
   public function insert($table,$data){
   //遍历数组，得到每一个字段和字段的值
   $key_str='';
   $v_str='';
   foreach($data as $key=>$v){
   // if(empty($v)){
   //  die("error");
   // }
    //$key的值是每一个字段s一个字段所对应的值
    $key_str.=$key.',';
    $v_str.="'$v',";
   }
   $key_str=trim($key_str,',');
   $v_str=trim($v_str,',');
   //判断数据是否为空
   $sql="insert into $table ($key_str) values ($v_str)";
   $this->query($sql);
  //返回上一次增加操做产生ID值
   return $this->getInsertid();
  }
  /*
  * 删除一条数据方法
  * @param1 $table, $where=array('id'=>'1') 表名 条件
  * @return 受影响的行数
  */
  public function deleteOne($table, $where){
   if(is_array($where)){
    foreach ($where as $key => $val) {
     $condition = $key.'='.$val;
    }
   } else {
    $condition = $where;
   }
   $sql = "delete from $table where $condition";
   $this->query($sql);
   //返回受影响的行数
   return mysqli_affected_rows($this->link);
  }
  /*
  * 删除多条数据方法
  * @param1 $table, $where 表名 条件
  * @return 受影响的行数
  */
  public function deleteAll($table, $where){
   if(is_array($where)){
    foreach ($where as $key => $val) {
     if(is_array($val)){
      $condition = $key.' in ('.implode(',', $val) .')';
     } else {
      $condition = $key. '=' .$val;
     }
    }
   } else {
    $condition = $where;
   }
   $sql = "delete from $table where $condition";
   $this->query($sql);
   //返回受影响的行数
   return mysqli_affected_rows($this->link);
  }
  /**
  * [修改操作description]
  * @param [type] $table [表名]
  * @param [type] $data [数据]
  * @param [type] $where [条件]
  * @return [type]
  */
  public function update($table,$data,$where,$limit=0){
   //遍历数组，得到每一个字段和字段的值
   $str='';
  foreach($data as $key=>$v){
   $str.="$key='$v',";
  }
  $str=rtrim($str,',');
   if(is_array($where)){
    foreach ($where as $key => $val) {
     if(is_array($val)){
      $condition = $key.' in ('.implode(',', $val) .')';
     } else {
      $condition = $key. '=' .$val;
     }
    }
   } else {
    $condition = $where;
   }
    if (!empty($limit)) {
      $limit = " limit ".$limit;
    }else{
      $limit='';
    }
  //修改SQL语句
  $sql="update $table set $str where $condition $limit";
  $this->query($sql);
  //返回受影响的行数
  return mysqli_affected_rows($this->link);
  }
}
?>