PHP单例模式简单用法示例

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：<?phpclassdb{public$

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：

<?php
class 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>";
?>