MYSQLI operation class

<?php 
/** 
* Mysqli类 
* 
* @author 废墟 
* @version v1.0 2009-08-18 
* @link http://anerg.cn/ 
*/ 
class db_mysqli { 
protected $mysqli; 
protected $sql; 
protected $rs; 
protected $query_num    = 0; 
protected $fetch_mode    = MYSQLI_ASSOC; 
protected $cache_dir    = &#39;./cache/&#39;; 
protected $cache_time    = 1800; 
public function  __construct($dbhost, $dbuser, $dbpass, $dbname) { 
$this->mysqli    = new mysqli($dbhost, $dbuser, $dbpass, $dbname); 
if(mysqli_connect_errno()) { 
$this->mysqli    = false; 
echo &#39;<h2>&#39;.mysqli_connect_error().&#39;</h2>&#39;; 
die(); 
} else { 
$this->mysqli->set_charset("utf8"); 
} 
} 
public function  __destruct() { 
$this->free(); 
$this->close(); 
} 
protected function free() { 
@$this->rs->free(); 
} 
protected function close() { 
$this->mysqli->close(); 
} 
protected function fetch() { 
return $this->rs->fetch_array($this->fetch_mode); 
} 
protected function getQuerySql($sql, $limit = null) { 
if (@preg_match("/[0-9]+(,[ ]?[0-9]+)?/is", $limit) && !preg_match("/ LIMIT [0-9]+(,[ ]?[0-9]+)?$/is", $sql)) { 
$sql .= " LIMIT " . $limit; 
} 
return $sql; 
} 
protected function get_cache($sql,$method) { 
include_once &#39;./cache.php&#39;;//若框架中使用__autoload()，这里可以不用加载文件 
$cache    = new cache($this->cache_dir,$this->cache_time); 
$cache_file    = md5($sql.$method); 
$res    = $cache->get_cache($cache_file); 
if(!$res) { 
$res    = $this->$method($sql); 
$cache->set_cache($cache_file, $res); 
} 
return $res; 
} 
public function query_num() { 
return $this->query_num; 
} 
public function set_cache_dir($cache_dir) { 
$this->cache_dir    = $cache_dir; 
} 
public function set_cache_time($cache_time) { 
$this->cache_time    = $cache_time; 
} 
public function query($sql, $limit = null) { 
$sql    = $this->getQuerySql($sql, $limit); 
$this->sql    = $sql; 
$this->rs    = $this->mysqli->query($sql); 
if (!$this->rs) { 
echo "<h2>".$this->mysqli->error."</h2>"; 
die(); 
} else { 
$this->query_num++; 
return $this->rs; 
} 
} 
public function getOne($sql) { 
$this->query($sql, 1); 
$this->fetch_mode    = MYSQLI_NUM; 
$row = $this->fetch(); 
$this->free(); 
return $row[0]; 
} 
public function get_one($sql) { 
return $this->getOne($sql); 
} 
public function cache_one($sql) { 
$sql    = $this->getQuerySql($sql, 1); 
return $this->get_cache($sql, &#39;getOne&#39;); 
} 
public function getRow($sql, $fetch_mode = MYSQLI_ASSOC) { 
$this->query($sql, 1); 
$this->fetch_mode    = $fetch_mode; 
$row = $this->fetch(); 
$this->free(); 
return $row; 
} 
public function get_row($sql, $fetch_mode = MYSQLI_ASSOC) { 
return $this->getRow($sql);
} 
public function cache_row($sql) { 
$sql    = $this->getQuerySql($sql, 1); 
return $this->get_cache($sql, &#39;getRow&#39;); 
} 
public function getAll($sql, $limit = null, $fetch_mode = MYSQLI_ASSOC) { 
$this->query($sql, $limit); 
$all_rows = array(); 
$this->fetch_mode    = $fetch_mode; 
while($rows = $this->fetch()) { 
$all_rows[] = $rows; 
} 
$this->free(); 
return $all_rows; 
} 
public function get_all($sql, $limit = null, $fetch_mode = MYSQLI_ASSOC) { 
return $this->getAll($sql); 
} 
public function cache_all($sql, $limit = null) { 
$sql    = $this->getQuerySql($sql, $limit); 
return $this->get_cache($sql, &#39;getAll&#39;); 
} 
public function insert_id() { 
return $this->mysqli->insert_id(); 
} 
public function escape($str) { 
if(is_array($str)) { 
foreach($str as $key=>$val) { 
$str[$key] = $this->escape($val); 
} 
} else { 
$str = addslashes(trim($str)); 
} 
return $str; 
} 
} 
//用法 
$db    = new db_mysqli(&#39;localhost&#39;, &#39;root&#39;, 111222, &#39;dict&#39;); 
$db->set_cache_time(10); 
$db->set_cache_dir(&#39;./cache/sql/&#39;); 
$sql = "select * from words order by word_id limit 10,10"; 
$res1 = $db->get_all($sql); 
$res2 = $db->cache_all($sql); 
echo $db->query_num(),&#39;<br>&#39;; 
?>