php 的代码看不懂怎么破

<?php
class Page{
    static $instances             = array();
    static $instancesByName     = array();
    static $instancesBySpecial   = array();
    function __construct($v,$byField=0,$fromRow=0,$pvq=0){
        # byField: 0=ID; 1=Name; 3=special
        if (!$byField && is_numeric($v)){ // by ID
            $r=$fromRow?$fromRow:($v?dbRow("select * from pages where id=$v limit 1"):array());
        }
        else if ($byField == 1){ // by name
            $name=strtolower(str_replace('-','_',$v));
            $fname='page_by_name_'.md5($name);
            $r=dbRow("select * from pages where name like '".addslashes($name)."' limit 1");
        }
        else if ($byField == 3 && is_numeric($v)){ // by special
            $fname='page_by_special_'.$v;
            $r=dbRow("select * from pages where special&$v limit 1");
        }
        else return false;
        if(!count($r || !is_array($r)))return false;
        if(!isset($r['id']))$r['id']=0;
        if(!isset($r['type']))$r['type']=0;
        if(!isset($r['special']))$r['special']=0;
        if(!isset($r['name']))$r['name']='NO NAME SUPPLIED';
        foreach ($r as $k=>$v) $this->{$k}=$v;
        $this->urlname=$r['name'];
        $this->dbVals=$r;
        self::$instances[$this->id] =& $this;
        self::$instancesByName[preg_replace('/[^a-z0-9]/','-',strtolower($this->urlname))] =& $this;
        self::$instancesBySpecial[$this->special] =& $this;
        if(!$this->vars)$this->vars='{}';
        $this->vars=json_decode($this->vars);
    }
    function getInstance($id=0,$fromRow=false,$pvq=false){
        if (!is_numeric($id)) return false;
        if (!@array_key_exists($id,self::$instances)) self::$instances[$id]=new Page($id,0,$fromRow,$pvq);
        return self::$instances[$id];
    }
    function getInstanceByName($name=''){
        $name=strtolower($name);
        $nameIndex=preg_replace('#[^a-z0-9/]#','-',$name);
        if(@array_key_exists($nameIndex,self::$instancesByName))return self::$instancesByName[$nameIndex];
        self::$instancesByName[$nameIndex]=new Page($name,1);
        return self::$instancesByName[$nameIndex];
    }
    function getInstanceBySpecial($sp=0){
        if (!is_numeric($sp)) return false;
        if (!@array_key_exists($sp,$instancesBySpecial)) $instancesBySpecial[$sp]=new Page($sp,3);
        return $instancesBySpecial[$sp];
    }
}