<?php
class DB {

	private $link_id;
	private $handle;
	private $is_log;
	private $time;

	//构造函数
	public function __construct($db_config = []) {
		$this->time = $this->microtime_float();
//		require(Spider_PATH."config/config.db.php");
		$this->connect($db_config["hostname"], $db_config["username"], $db_config["password"], $db_config["database"], $db_config["pconnect"]);
		$this->is_log = $db_config["log"];
		if($this->is_log){
			$handle = fopen($db_config["logfilepath"]."dblog.txt", "a+");
			$this->handle=$handle;
		}
	}
	
	//数据库连接
	public function connect($dbhost, $dbuser, $dbpw, $dbname, $pconnect = 0,$charset='utf8') {
		if( $pconnect==0 ) {
			$this->link_id = @mysqli_connect($dbhost, $dbuser, $dbpw, $dbname);
			if(!$this->link_id){
				$this->halt("数据库连接失败");
			}
		} else {
			$this->link_id = @mysqli_connect('p:'.$dbhost, $dbuser, $dbpw,$dbname);
			if(!$this->link_id){
				$this->halt("数据库持久连接失败");
			}
		}
		//if(!@mysqli_select_db($dbname,$this->link_id)) {
		//	$this->halt('数据库选择失败');
		//}
		@mysqli_query($this->link_id,"set names ".$charset);
	}
	
	public function ping(){ 
		if(!mysqli_ping($this->link_id)){ 
			$this->close();
			//mysqli_close($this->link_id); //注意：一定要先执行数据库关闭，这是关键 
			require("config.db.php");
		/*	
//			$db_config["hostname"] = "127.0.0.1"; //服务器地址
//			$db_config["username"] = "root"; //数据库用户名
//			$db_config["password"] = ""; //数据库密码
//			$db_config["database"] = "spell"; //数据库名称
//			$db_config["charset"] = "utf8";//数据库编码
//			$db_config["pconnect"] = 1;//开启持久连接
//			$db_config["log"] = 0;//开启日志
//			$db_config["logfilepath"] = './';//开启日志*/
			$this->connect($db_config["hostname"], $db_config["username"], $db_config["password"], $db_config["database"], $db_config["pconnect"]);
		
		$this->is_log = $db_config["log"];
		if($this->is_log){
			$handle = fopen($db_config["logfilepath"]."dblog.txt", "a+");
			$this->handle=$handle;
		}
		
		} 
	} 

	//查询 
	public function query($sql) {
		$this->write_log("查询 ".$sql);
		$this->ping();
		$query = mysqli_query($this->link_id,$sql);
		if(!$query) $this->halt('Query Error: ' . $sql);
		return $query;
	}
	
	//获取一条记录（MYSQL_ASSOC，MYSQL_NUM，MYSQL_BOTH）				
	public function get_one($sql,$result_type = MYSQLI_ASSOC) {
		$query = $this->query($sql);
		$rt = mysqli_fetch_array($query,$result_type);
		$this->write_log("获取一条记录 ".$sql);
		return $rt;
	}

	//获取全部记录
	public function get_all($sql,$result_type = MYSQLI_ASSOC) {
		$query = $this->query($sql);
		$i = 0;
		$rt = array();
		while($row = mysqli_fetch_array($query,$result_type)) {
			$rt[$i]=$row;
			$i++;
		}
		$this->write_log("获取全部记录 ".$sql);
		return $rt;
	}
	
	//插入
	public function insert($table,$dataArray) {
		$field = "";
		$value = "";
		if( !is_array($dataArray) || count($dataArray)<=0) {
			$this->halt('没有要插入的数据');
			return false;
		}
		while(list($key,$val)=each($dataArray)) {
			$field .="$key,";
			$value .="'$val',";
		}
		$field = substr( $field,0,-1);
		$value = substr( $value,0,-1);
		$sql = "insert into $table($field) values($value)";
		$this->write_log("插入 ".$sql);
		if(!$this->query($sql)) return false;
		return true;
	}

	//更新
	public function update( $table,$dataArray,$condition="") {
		if( !is_array($dataArray) || count($dataArray)<=0) {
			$this->halt('没有要更新的数据');
			return false;
		}
		$value = "";
		while( list($key,$val) = each($dataArray)) {
			$value .= "$key = '$val',";
		}
        $value = substr( $value,0,-1);
		if($condition){
			$sql = "update $table set $value where 1=1 and $condition";
		}else{
			$sql = "update $table set $value where 1=1";
		}
		$this->write_log("更新 ".$sql);
		if(!$this->query($sql)) return false;
		return true;
	}

	//删除
	public function delete( $table,$condition="") {
		if( empty($condition) ) {
			$this->halt('没有设置删除的条件');
			return false;
		}
		$sql = "delete from $table where 1=1 and $condition";
		$this->write_log("删除 ".$sql);
		if(!$this->query($sql)) return false;
		return true;
	}

	//返回结果集
	public function fetch_array($query, $result_type = MYSQLI_ASSOC){
		$this->write_log("返回结果集");
		return mysqli_fetch_array($query, $result_type);
	}

	//获取记录条数
	public function num_rows($results) {
		if(!is_bool($results)) {
			$num = mysqli_num_rows($results);
			$this->write_log("获取的记录条数为".$num);
			return $num;
		} else {
			return 0;
		}
	}

	//释放结果集
	public function free_result() {
		$void = func_get_args();
		foreach($void as $query) {
			if(is_resource($query) && get_resource_type($query) === 'mysql result') {
				return mysqli_free_result($query);
			}
		}
		$this->write_log("释放结果集");
	}

	//获取最后插入的id
	public function insert_id() {
		$id = mysqli_insert_id($this->link_id);
		$this->write_log("最后插入的id为".$id);
		return $id;
	}

	//关闭数据库连接
	protected function close() {
		$this->write_log("已关闭数据库连接");
		return @mysqli_close($this->link_id);
	}

	//错误提示
	private function halt($msg='') {
		$msg .= "\r\n".mysqli_error($this->link_id);
		$this->write_log($msg);
		die($msg);
	}

	//析构函数
	public function __destruct() {
		$this->free_result();
		$use_time = ($this-> microtime_float())-($this->time);
		$this->write_log("完成整个查询任务,所用时间为".$use_time);
		if($this->is_log){
			fclose($this->handle);
		}
	}
	
	//写入日志文件
	public function write_log($msg=''){
		if($this->is_log){
			$text = date("Y-m-d H:i:s")." ".$msg."\r\n";
			fwrite($this->handle,$text);
		}
	}
	
	//获取毫秒数
	public function microtime_float() {
		list($usec, $sec) = explode(" ", microtime());
		return ((float)$usec + (float)$sec);
	}
}

?>

使用

//config里自定义sql配置信息
$db = new DB($config['mysql']);
$sql = 'SQL语句';
$db->get_one($sql);