== 与 === 导致的性能差异

<?php
/**   分页类 **/                                                                                                                                                                                                                
class Application_Model_DbTable_Page{
    public $up_page;
    public $next_page;
    public $count_page;
    public $count_record;
    public $prefix;
    public $suffix;
   
    public $limit;
    public $current_page;
    public $sql;
    public $db;
    public $queryWhere;
   
    public $data;
   
   
    function __construct($current_page=1,$sql="",$limit=10) {
        $this->current_page = $current_page;
        $this->sql = $sql;
        $this->limit = $limit;
        $this->db = Zend_Db_Table::getDefaultAdapter();
    }
   
   
    function getData(){
        return $this->data;
    }
    function setData($data){
        $this->data = $data;
    }
   
    function setLimit($limit){
        $this->limit = $limit;
    }
    function setSql($sql){
        $this->sql = $sql;
    }
   
    function setCurentPage($current_page){
        $this->current_page = $current_page;
    }
   
    function getPageAttr(){
        return array(
            "count_record"=>$this->getCountRecord(),
            "count_page"=>$this->getCountPage(),
            "current_page"=>$this->getCurrentPage(),
            "up_page"=>$this->getUpPage(),
            "next_page"=>$this->getNextPage(),
            "limit"=>$this->getLimit(),
            "sql"=>$this->getSql(),
            "prefix"=>$this->getPrefix(),
            "data"=>$this->getData()
        );
    }
   
    function getCurrentPage(){
        if($this->current_page == '' || $this->current_page === null){
            $this->current_page = 1;
        }
        if($this->current_page<=1){
            $this->current_page = 1;
        }
        if($this->current_page>=$this->getCountPage()){
            $this->current_page = $this->getCountPage();
        }
        return $this->current_page;
    }
   
    function getCountPage(){
        return $this->count_page = ceil($this->getCountRecord()/$this->getLimit());
    }
    function getCountRecord(){

       /** if($this->count_record == null){  这是之前的写法。因为记录条数可能为  0，而为零的时候，导致这 0==null 每调用一次该方法时，就去查询数据库，所以引起效率底下！。*/

       //
        if($this->count_record === null){       
            $db = $this->getDB();
            $sql = $this->getSql();
            $result = $db->fetchAll ( $sql );
            $this->count_record = count($result);
        }
        return $this->count_record;
    }
    function getDB(){
        if($this->db === null){
            $this->db = Zend_Db_Table::getDefaultAdapter();
        }
        return $this->db;
    }
   
    function getSql(){
        return $this->sql;
    }
   
    function getUpPage(){
        if($this->getCurrentPage() - 1 < 1){
            $this->up_page = 1;
        }else{
            $this->up_page = $this->getCurrentPage() - 1;
        }
        return $this->up_page;
    }
    function getNextPage(){
           if($this->getCurrentPage() + 1 > $this->getCountPage()){
            $this->next_page = $this->getCountPage();
        }else{
            $this->next_page = $this->getCurrentPage() + 1;
        }
        return $this->next_page;
    }
   
    function getLimit(){
        if($this->limit == '' || $this->limit === null){
            $this->limit = 10;
        }
        return $this->limit;
    }
   
    function getPrefix(){
        if(($this->getCurrentPage()-1)<0){
            $this->prefix = 0;
        }else{
            $this->prefix = ($this->getCurrentPage()-1) * $this->getLimit();
        }
        return $this->prefix;
    }
}