[PHP]

function connect(){

if( 0 == $this->link_id ){

$this->link_id=@mysql_connect($this->server,$this->user,$this->password);

if( $this->database!="" ){

@mysql_select_db($this->database, $this->link_id);

}

}

}

[/PHP]

为什么不是 $this->link_id==0 而是 0==$this->link_id,有什么区别啊