本文实例讲述了PHP单例模式用法。分享给大家供大家参考，具体如下：

<?phpclass db { public $conn; public static $sql; public static $instance=null; private function __construct(){ require_once('db.config.php'); $this->conn = mysql_connect($db['host'],$db['user'],$db['password']); if(!mysql_select_db($db['database'],$this->conn)){ echo "失败"; }; mysql_query('set names utf8',$this->conn); } public static function getInstance(){ if(is_null(self::$instance)){ self::$instance = new self(); } return self::$instance; } /** * 查询数据库 */ public function select($table,$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); $resuleRow = array(); $i = 0; while($row=mysql_fetch_assoc($result)){ foreach($row as $k=>$v){ $resuleRow[$i][$k] = $v; } $i++; } return $resuleRow; } //添加一条记录 public function insert($table,$data) { $values = ''; $data = ''; foreach ($data as $k=>$v) { $values .= $k.','; $datas .= "'$v'".','; } $values = rtrim($values,','); $datas = rtrim($datas,','); self::$sql = "INSERT INTO {$table} ({$values}) VALUES ({$datas})"; if(mysql_query(self::$sql)) { return mysql_insert_id(); } else { return false; } } //修改一条记录 public function update($table,$data,$condition=array()){ $where=''; if(!empty($condition)) { foreach($condition as $k=>$v) { $where.=$k."='".$v."' and "; } $where='where '.$where .'1=1'; } $updatastr = ''; if(!empty($data)) { foreach($data as $k=>$v) { $updatastr.= $k."='".$v."',"; } $updatastr = 'set '.rtrim($updatastr,','); } self::$sql = "update {$table} {$updatastr} {$where}"; return mysql_query(self::$sql); } //删除记录 public function delete($table,$condition) { $where=''; if(!empty($condition)) { foreach($condition as $k=>$v) { $where.=$k."='".$v."' and "; } $where='where '.$where .'1=1'; } self::$sql = "delete from {$table} {$where}"; return mysql_query(self::$sql); } public static function getLastSql() { echo self::$sql; }}$db = db::getInstance();//$list = $db->select('demo',array('name'=>'tom','password'=>'ds'),array('name','password'));//echo $db->insert('demo',array('name'=>'最近你啦','password'=>'123'));//echo $db->update('demo',array("name"=>'xxx',"password"=>'123'),array('id'=>1));echo $db->delete('demo',array('id'=>'2'));db::getLastSql();echo "<pre>";?>

更多关于PHP相关内容感兴趣的读者可查看本站专题：《php面向对象程序设计入门教程》、《PHP基本语法入门教程》、《PHP网络编程技巧总结》、《PHP数组(Array)操作技巧大全》、《php字符串(string)用法总结》、《php+mysql数据库操作入门教程》及《php常见数据库操作技巧汇总》

希望本文所述对大家PHP程序设计有所帮助。