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：
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<?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>";
?>
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希望本文所述对大家PHP程序设计有所帮助。