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：

<?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>";
?>

希望本文所述对大家PHP程序设计有所帮助。