PHP Single-instance mode

Single-Case mode
Singleton mode is useful when you need to ensure that an object can have only one instance. It delegates control of the created object to a single point, and at any time the application will only have one instance to exist.

The singleton pattern must contain: private constructor, static variable, public static method, private Clone method.

Here's a chestnut.

<?PHP/** MySQL single case*/class MySQL{    Private $host= ' Yourhost ';//Database Host    Private $user= ' Youruser ';//Database user name    Private $pwd= ' yourpwd ';//database user name password    Private $database= ' database ';//Database name    Private $charset= ' UTF8 ';//database encoding, gbk,utf8,gb2312    Private $link;//database connection identification;    Private $rows;//multi-row array obtained by query    Static $_instance;//Storage Objects    /** * Private Constructors*/    Private function__construct ($pconnect=false) {        if(!$pconnect) {            $this->link = @mysql_connect($this->host,$this->user,$this-&GT;PWD) or$this-err (); } Else {            $this->link = @Mysql_pconnect($this->host,$this->user,$this-&GT;PWD) or$this-err (); }        mysql_select_db($this->database) or$this-err (); $this->query ("SET NAMES ' {$this->charset} ' ",$this-link); return $this-link; }    /** * Prevent cloning **/    Private function__clone () {} Public Static functionGetInstance ($pconnect=false){        if(FALSE= = (self::$_instanceinstanceof Self)) { Self::$_instance=NewSelf$pconnect); }        returnSelf::$_instance; }    /** * Enquiry*/     Public functionQuery$sql,$link= ' ') {        $this->result =mysql_query($sql,$this->link) or$this->err ($sql); return $this-result; }    /** * Single record*/     Public functionGetRow ($sql,$type=Mysql_assoc) {        $result=$this->query ($sql); return@Mysql_fetch_array($result,$type); }    /** * Multi-line record*/     Public functionGetRows ($sql,$type=Mysql_assoc) {        $result=$this->query ($sql);  while($row= @Mysql_fetch_array($result,$type)) {            $this->rows[] =$row; }        return $this-rows; }    /** * error message output*/    protected functionErr$sql=NULL) {            }}//Use Cases$db=MySQL::getinstance ();$db 2=MySQL::getinstance ();$data=$db->getrows (' select * FROM blog ');//Print_r ($data);//Determine if two objects are equalif($db===$db 2){    Echo' True ';}?>

PHP Single-instance mode