php单例模式应用于mysql数据库操作

来源：互联网发布：office办公软件教材编辑：程序博客网时间：2024/06/03 21:38

PHP中有很多的数据库操作，使用单例模式进行数据库的操作，可以避免大量的new操作浪费资源；

使用单例模式可以很方便的实现一个类来全局控制某些配置信息；

单例模式的要点有三个：

一是某个类只能有一个实例；
二是它必须自行创建这个实例；
三是它必须自行向整个系统提供这个实例。

下里面来一个数据库操作的单例模式实例：

class db{public $conn;public static $sql;public static $intance = null;protected $host;protected $user;protected $pass;protected $database;protected $charset;public function __construct($host, $user, $pass, $database, $charset){$this->host = $host;$this->user = $user;$this->pass = $pass;$this->database = $database;$this->charset = $charset;$this->conn = mysql_connect($this->host, $this->user, $this->pass);if(!mysql_select_db($this->database, $this->conn)){die('mysql connect failed');}mysql_query('set name '.$this->charset, $this->conn);}public static function getIntance(){if(is_null(self::$intance)){self::$intance = new db($this->host, $this->user, $this->pass, $this->database, $this->charset);}return self::$intance;}/** *@param string $table *@param array $condition  *@param array $field *@return array  */public function getRows($table, $condition=array(), $field=array()){$where = '';if(!empty($condition)){foreach ($condition as $k=>$v){$where .= $k."='".$v."' and";}$where = 'where '.$where.' 1=1';}$fieldStr = '';if(!empty($field)){foreach ($field as $k=>$v){$fieldStr .= $v.',';}$fieldStr = rtrim($fieldStr, ',');}else{$fieldStr = "*";}self::$sql = "select {$fieldStr} from {$table} {$where}";$result = mysql_query(self::$sql, $this->conn);$resultRow = array();$i = 0;while($row = mysql_fetch_assoc($result)){foreach ($row as $k=>$v){$resultRow[$i][$k] = $v;}$i++;}return $resultRow;}/** * @param string $table * @param array $data * @param array $condition * @return boolean */public function update($table, $data=array(), $condition=array()){$where = '';if(!empty($condition)){foreach ($condition as $key=>$val){$where .= $key."='".$val."' and ";}$where = 'where '.$where .' 1=1';}$updateStr = '';if(!empty($data)){foreach ($data as $key=>$val){$updateStr .= $key." = '".$val."' ,";}$updateStr = 'set '.rtrim($updateStr, ',');}self::$sql = "update {$table} {$updateStr} {$where}";return mysql_query(self::$sql, $this->conn);}/** *  * @param string $table * @param array $data * @return number|boolean */public function insert($table, $data=array()){$fields = '';$value = '';if(!empty($data)){foreach ($data as $k=>$v){$fields .= $k.',';$value .= "'$v'".',';}$fields = rtrim($fields, ',');$value = rtrim($value, ',');}else{die($data.' is not allowed empty!');}self::$sql = "insert into {$table} ({$fields}) values({$value})";if(mysql_query(self::$sql, $this->conn)){return mysql_insert_id();}else{return false;}}/** *  * @param string $table * @param array $condition * @return resource */public function delete($table, $condition=array()){$where = '';if(!empty($condition)){foreach ($condition as $k=>$v){$where .= $k." = '".$v."', ";}$where = " where ".$where." 1=1";}self::$sql = "delete from {$table} {$where}";return mysql_query(self::$sql, $this->conn);}}

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