自己动手做一个SQL解释器

这是从别的地方看到的，俺还不会写这么无聊的东西

<?php

class DB_text {
var $conn;
var $classname = "db_text";
var $database;
function on_create() {
}
function connect($database_name) {
$this->database = $database_name;
if(! file_exists($database_name)) {
$this->conn = array();
$this->_close();
}
$fp = fopen($this->database,"r");
$this->conn = unserialize(fread($fp,filesize($this->database)));
fclose($fp);
}
function &query($query) {
if(eregi("select ",$query)) return $this->_select($query);
if(eregi("insert ",$query)) return $this->_insert($query);
if(eregi("delete ",$query)) return $this->_delete($query);
if(eregi("update ",$query)) return $this->_update($query);
return array();
}
function fetch_row(&$result) {
if(list($key,$value) = each($result))
return $value;
return false;
}
function num_rows($result) {
return count($result);
}

/**
* query的辅助函数
*/
function _select($query) {
if(eregi("(order by (. ))",$query,$regs)) {
$order = $regs[2];
$query = eregi_replace($regs[1],"",$query);
}
if(eregi("(group by (. ))",$query,$regs)) {
$group = $regs[2];
$query = eregi_replace($regs[1],"",$query);
}
eregi("select .* from ([0-9a-z_] ) *(where (. ))?",$query,$regs);
if($regs[3] != "") {
$keys = $this->_where($regs[3],"$this->conn[$regs[1]]");
while(list($key,$value) = each($keys)) {
$rs[] = $this->conn[$regs[1]][$value];
}
}else {
$rs = $this->conn[$regs[1]];
}
if($order) {
sscanf($order,"%s %s",$key,$type);
if(empty($type)) $type = "asc";
$this->_sort($rs,$key,$type);
}
return $rs;

传递数组时使用 return 比使用 global 要高效，比如：

function userloginfo($usertemp){

$detail=explode("",$usertemp);

return $detail;

}

$login=userloginfo($userdb);

比

function userloginfo($usertemp){

global $detail;

$detail=explode("",$usertemp);

}

userloginfo($userdb);

要高效

二、 (这个代码用于得到程序目录对应的网址,推荐使用)

$urlarray=explode('/',$HTTP_SERVER_VARS['REQUEST_URI']);

$urlcount=count($urlarray);unset($urlarray[$urlcount-1]);

$ofstarurl='http://'.$HTTP_SERVER_VARS['HTTP_HOST'].implode('/',$urlarray);

这段代码比

$pre_urlarray=explode('/',$HTTP_SERVER_VARS['HTTP_REFERER']);

$pre_url=array_pop($pre_urlarray);

要高效

三、 在循环中判定时,数值判定使用恒等要比等于高效

$a=2;$b=2;

假如使用 iconv() 函数转换编码就相比比较简单了，不过很多虚拟主机里并不支持这个组件，我在网上找半天，才找到一个gb2312转utf-8的方法，但不能逆向转换。

这个函数如下：

/*******************************
//GB转UTF-8编码
*******************************/
function gb2utf8($gbstr) {
global $CODETABLE;
if(trim($gbstr)=="") return $gbstr;
if(empty($CODETABLE)){
$filename = dirname(__FILE__)."/gb2312-utf8.table";
$fp = fopen($filename,"r");
while ($l = fgets($fp,15))
{ $CODETABLE[hexdec(substr($l, 0, 6))] = substr($l, 7, 6); }
fclose($fp);
}
$ret = "";
$utf8 = "";
while ($gbstr) {
if (ord(substr($gbstr, 0, 1)) > 127) {
$thisW = substr($gbstr, 0, 2);
$gbstr = substr($gbstr, 2, strlen($gbstr));
$utf8 = "";
@$utf8 = u2utf8(hexdec($CODETABLE[hexdec(bin2hex($thisW)) - 0x8080]));
if($utf8!=""){
for ($i = 0;$i < strlen($utf8);$i = 3)
$ret .= chr(substr($utf8, $i, 3));
}
}
else
{
$ret .= substr($gbstr, 0, 1);
$gbstr = substr($gbstr, 1, strlen($gbstr));
}
}
return $ret;
}
//Unicode转utf8
function u2utf8($c) {
for ($i = 0;$i < count($c);$i )
$str = "";
if ($c < 0x80) {
$str .= $c;
} else if ($c < 0x800) {
$str .= (0xC0 | $c >> 6);
$str .= (0x80 | $c & 0x3F);
} else if ($c < 0x10000) {
$str .= (0xE0 | $c >> 12);
$str .= (0x80 | $c >> 6 & 0x3F);
$str .= (0x80 | $c & 0x3F);
} else if ($c < 0x200000) {
$str .= (0xF0 | $c >> 18);
$str .= (0x80 | $c >> 12 & 0x3F);
$str .= (0x80 | $c >> 6 & 0x3F);
$str .= (0x80 | $c & 0x3F);
}

用 $_SERVER[SERVER_NAME].$_SERVER[PHP_SELF] 参数和端口取不到

//写了一个函数，获得当前页面的绝对的Url(可能的https，端口，以及参数)
function AbsoluteUrl() {
GLOBAL $HTTP_SERVER_VARS;
$HTTPS =$HTTP_SERVER_VARS["HTTPS"];
$HTTP_HOST =$HTTP_SERVER_VARS["HTTP_HOST"];
$script_URL =$HTTP_SERVER_VARS["script_URL"];
$PATH_INFO =$HTTP_SERVER_VARS["PATH_INFO"];
$REQUEST_URI=$HTTP_SERVER_VARS["REQUEST_URI"];
$script_NAME=$HTTP_SERVER_VARS["script_NAME"];

$QUERY_STRING=$HTTP_SERVER_VARS["QUERY_STRING"];
if (get_magic_quotes_gpc()==1) $QUERY_STRING=stripslashes($QUERY_STRING);
if ($QUERY_STRING!="") $QUERY_STRING="?".$QUERY_STRING;

$uri_http=(((strtolower($HTTPS)=="off")or($HTTPS==0)) ? 'http' : 'https') . '://' . $HTTP_HOST;

if (isset($script_URL))
$url=$script_URL;

else if (isset($PATH_INFO))
$url = $PATH_INFO;

else if (isset($REQUEST_URI))
$url = $REQUEST_URI;

else if (isset($script_NAME))
$url = $script_NAME;

$url=$uri_http.$url.$QUERY_STRING;

return $url;
}

<?php
//定义输出为图像类型
header("content-type:image/gif");
//新建图象
$pic=imagecreate(240,30);
//定义黑白颜色
$black=imagecolorallocate($pic,0,0,0);
$white=imagecolorallocate($pic,255,255,255);
//定义字体
$font="c://WIN2000//fonts//simhei.ttf";
//定义输出字体串
$str = chr(0xE8).chr(0xB5).chr(0x9B).chr(0xE8).chr(0xBF).chr(0xAA).chr(0xE7).chr(0xBD).chr(0x91)." www.ccidnet.com";
//写 TTF 文字到图中
imagettftext($pic,20,0,10,20,$white,$font,$str);
//建立 GIF 图型
imagegif($pic);
//结束图形，释放内存空间
imagedestroy($pic);
?>