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本文實(shí)例講述了PHP單例模式用法。分享給大家供大家參考，具體如下：

<?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 "失敗";
    };
    mysql_query('set names utf8',$this->conn);
  }
  public static function getInstance(){
  if(is_null(self::$instance)){
    self::$instance = new self();
  }
    return self::$instance;
  }
  /**
  * 查詢(xún)數(shù)據(jù)庫(kù)
  */
  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 $resuleRow;
  }
  //添加一條記錄
  public function insert($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::$sql)) {
      return mysql_insert_id();
    } else {
      return false;
    }
  }
  //修改一條記錄
  public function update($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::$sql);
  }
  //刪除記錄
  public function delete($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>";
?>

更多關(guān)于PHP相關(guān)內(nèi)容感興趣的讀者可查看本站專(zhuān)題：《php面向?qū)ο蟪绦蛟O(shè)計(jì)入門(mén)教程》、《PHP基本語(yǔ)法入門(mén)教程》、《PHP網(wǎng)絡(luò)編程技巧總結(jié)》、《PHP數(shù)組(Array)操作技巧大全》、《php字符串(string)用法總結(jié)》、《php+mysql數(shù)據(jù)庫(kù)操作入門(mén)教程》及《php常見(jiàn)數(shù)據(jù)庫(kù)操作技巧匯總》

希望本文所述對(duì)大家PHP程序設(shè)計(jì)有所幫助。