Short URL exploration, URL exploration_PHP tutorial

Short URL exploration, URL exploration

Introduction

Short URLs are common, such as the following

　http://dwz.cn/CSW6Y => http://www.cnblogs.com/iforever/p/4313704.html,

　http://dwz.cn/CSWuP => http://www.cnblogs.com/iforever/p/4279006.html, etc.

When accessing these URLs, the front and back pairs point to the same page. I am just giving an example. These short URLs are often seen in weibo or similar social networks. Since the original link address is particularly long, this time the short URL is short. The URL will show its power and be short and easy to remember, but it also has its shortcomings. For example, short URLs may not directly see some information in the URL (some information can be seen in long URLs).

I have been exposed to this all day long, so that before I really understand its principle, it has imprinted "nothing" in my mind. This has missed some knowledge. This situation should be called in psychology. I'm thinking, does anyone know that this is the case?

Principle

First of all, I guess this is achieved through redirection. dwz.cn is a server used to receive some short URLs. These short URLs are processed by dwz.cn and have corresponding short URLs in dwz.cn. The record of the long URL, then obtain the long URL corresponding to the short URL from the database, and then redirect with 302. See if this is the case.

Visit http://dwz.cn/CSW6Y through the browser and analyze the request (use Chrome’s debugging tool here, or you can use tools such as wireshark), and you can get the following data:

name: abit version: 1 handle: - rewrite: if (!-d && !-f && path ~ "/(.*)$") goto "do.php?url=$1&act=out"

Handle: The following are the rewrite rules. For the specific detailed rules of Sina Cloud, please see here http://sae.sina.com.cn/doc/php/runtime.html#php-app-config. It is very simple. The configurations of nginx and apache are also similar.

Another thing to note after the redirection is completed is that urlencode must be performed when passing parameters, and urldecode must be used before redirection. When url type parameters are passed without using urlencode, part of the information may be lost when obtained. Therefore, when passing parameters before generating a short link, the URL must be escaped, the special string must be encoded, and the short link must be processed when accessing. It is necessary to urldecode the encoded URL and restore it to a normal link. Otherwise, the link will not be regarded as a normal URL when the header jumps. After the jump, the URL will be appended to the host of the previous page, similar to http://abit.sinaapp.com/www.cnblogs.com, errors may occur, so please pay special attention here.

There will be a problem when sae redirects, double backslashes will be automatically filtered into one, for example from http://abit.sinaapp.com/ to http:/abit.sinaapp.com/, please note , there is a missing backslash here, you should pay special attention to this when processing, otherwise you may encounter unnecessary trouble.

Encoding

Main processing part

<?<span>php
</span><span>class</span><span> snapshotUrl{
    </span><span>//</span><span>进行编码的数据库，没6位二进制数对应一个字符，一共需要64位，因此选取
    //52+10+2个特殊字符</span>
    <span>private</span> <span>static</span> <span>$basedb</span> = <span>array</span><span>(
        </span>'(',')','a','b','c','d',
        'e','f','g','h','i','j',
        'k','l','m','n','o','p',
        'q','r','s','t','u','v',
        'w','x','y','z','A','B',
        'C','D','E','F','G','H',
        'I','J','K','L','M','N',
        'O','P','Q','R','S','T',
        'U','V','W','X','Y','Z',
        '0','1','2','3','4','5',
        '6','7','8','9',<span>
    );

    </span><span>private</span> <span>function</span> long2short(<span>$url</span><span>){
        </span><span>$hex</span> = <span>md5</span>(<span>$url</span><span>);
        </span><span>$out</span> = ''<span>;
        </span><span>$hex</span> = 0x7FFFFFFF & (1 * ('0x'.<span>substr</span>(<span>$hex</span>, 0, 8<span>)));
        </span><span>for</span>(<span>$i</span>=0; <span>$i</span><5; <span>$i</span>++<span>){
            </span><span>$index</span> = 0x3f & <span>$hex</span><span>;
            </span><span>$out</span> .= self::<span>$basedb</span>[<span>$index</span><span>];
            </span><span>$hex</span> = <span>$hex</span>>>6<span>;
        }
        </span><span>return</span> <span>$out</span><span>;
    }

    </span><span>public</span> <span>function</span> retJson(<span>$arr</span><span>){
        </span><span>return</span> json_encode(<span>$arr</span><span>);
    }

    </span><span>//</span><span>对url进行映射保存</span>
    <span>public</span> <span>function</span> dispose(<span>$url</span>, <span>$act</span><span>){
        </span><span>$mysql</span> = <span>new</span><span> SaeMysql();
        </span><span>switch</span> (<span>$act</span><span>) {
            </span><span>case</span> 'in':
                <span>$short</span> = <span>$this</span>->long2short(<span>$url</span><span>);
                </span><span>$url</span> = <span>addslashes</span>(<span>$url</span><span>);
                </span><span>$sql</span> = "insert into `tiny_url`(`short`,`long`) values ('{<span>$short</span>}','{<span>$url</span>}')"<span>;
                </span><span>$mysql</span>->runSql(<span>$sql</span><span>);
                </span><span>if</span>(<span>$mysql</span>->errno() != 0<span>){
                    </span><span>echo</span> "生成失败"<span>;
                }</span><span>else</span><span>{
                    </span><span>echo</span> "http://abit.sinaapp.com/{<span>$short</span>}"<span>;
                }
                </span><span>break</span><span>;
            </span><span>case</span> 'out':
                <span>if</span>(<span>strlen</span>(<span>$url</span>) > 5<span>)
                    </span><span>echo</span> <span>$this</span>->retJson(<span>array</span>("code"=>"-1","msg"=>"没有这条记录"<span>));
                </span><span>$sql</span> = "select * from `tiny_url` where `short`='{<span>$url</span>}' limit 1"<span>;
                </span><span>$data</span> = <span>$mysql</span>->getData(<span>$sql</span><span>);
                </span><span>if</span>(!<span>$data</span><span>) {
                    </span><span>echo</span> <span>$this</span>->retJson(<span>array</span>("code"=>"-1","msg"=>"没有这条记录"<span>));
                }</span><span>else</span><span>{
                    </span><span>$location</span> = <span>urldecode</span>(<span>$data</span>[0]['long'<span>]);
                    </span><span>header</span>("Location: {<span>$location</span>}"<span>);
                    </span><span>exit</span><span>();
                }
                </span><span>break</span><span>;

            </span><span>default</span>:
                <span>#</span><span> code...</span>
                <span>break</span><span>;
        }
    }
}

</span><span>$url</span> = <span>isset</span>(<span>$_GET</span>['url']) ? <span>$_GET</span>['url'] : <span>null</span><span>;
</span><span>$act</span> = <span>isset</span>(<span>$_GET</span>['act']) ? <span>$_GET</span>['act'] : <span>null</span><span>;
</span><span>$snapshotUrl</span> = <span>new</span><span> snapshotUrl();
</span><span>if</span>(<span>$url</span> === <span>null</span> || <span>$act</span> === <span>null</span><span>)
    </span><span>echo</span> <span>$snapshotUrl</span>->retJson(<span>array</span>("code"=>"-1","msg"=>"参数错误"<span>));

</span><span>$snapshotUrl</span>->dispose(<span>$url</span>, <span>$act</span>);

Results

I made a small webpage that can be tested:

　http://abit.sinaapp.com/ If you are interested, you can try it

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