PHP利用正则表达式将相对路径转成绝对路径的方法示例

2024-02-28 17:07:13 195

前言

大家应该都有所体会，很多时候在做网络爬虫的时候特别需要将爬虫搜索到的超链接进行处理，统一都改成绝对路径的，所以本文就写了一个正则表达式来对搜索到的链接进行处理。下面话不多说，来看看详细的介绍吧。

通常我们可能会搜索到如下的链接：

<!--空超链接-->
<ahref=""></a>
<!--空白符-->
<ahref=""rel="externalnofollow"></a>
<!--a标签含有其它属性-->
<ahref="index.html"rel="externalnofollow"rel="externalnofollow"rel="externalnofollow"alt="超链接">index.html</a>
<ahref="/"rel="externalnofollow"rel="externalnofollow"rel="externalnofollow"rel="externalnofollow"target="_blank">/target="_blank"</a>
<atarget="_blank"href="/"rel="externalnofollow"rel="externalnofollow"rel="externalnofollow"rel="externalnofollow"alt="超链接">target="_blank"/alt="超链接"</a>
<atarget="_blank"title="超链接"href="/"rel="externalnofollow"rel="externalnofollow"rel="externalnofollow"rel="externalnofollow"alt="超链接">target="_blank"title="超链接"/alt="超链接"</a>
<!--根目录-->
<ahref="/"rel="externalnofollow"rel="externalnofollow"rel="externalnofollow"rel="externalnofollow">/</a>
<ahref="a"rel="externalnofollow">a</a>
<!--含参数-->
<ahref="/index.html?id=1"rel="externalnofollow">/index.html?id=1</a>
<ahref="?id=2"rel="externalnofollow">?id=2</a>
<!--//-->
<ahref="//index.html"rel="externalnofollow">//index.html</a>
<ahref="//www.mafutian.net"rel="externalnofollow">//www.mafutian.net</a>
<!--站内链接-->
<ahref="http://www.hole_1.com/index.html"rel="externalnofollow">http://www.hole_1.com/index.html</a>
<!--站外链接-->
<ahref="http://www.mafutian.net"rel="externalnofollow">http://www.mafutian.net</a>
<ahref="http://www.numberer.net"rel="externalnofollow">http://www.numberer.net</a>
<!--图片，文本文件格式的链接-->
<ahref="1.jpg"rel="externalnofollow">1.jpg</a>
<ahref="1.jpeg"rel="externalnofollow">1.jpeg</a>
<ahref="1.gif"rel="externalnofollow">1.gif</a>
<ahref="1.png"rel="externalnofollow">1.png</a>
<ahref="1.txt"rel="externalnofollow">1.txt</a>
<!--普通链接-->
<ahref="index.html"rel="externalnofollow"rel="externalnofollow"rel="externalnofollow">index.html</a>
<ahref="index.html"rel="externalnofollow"rel="externalnofollow"rel="externalnofollow">index.html</a>
<ahref="./index.html"rel="externalnofollow">./index.html</a>
<ahref="../index.html"rel="externalnofollow">../index.html</a>
<ahref=".../"rel="externalnofollow">.../</a>
<ahref="..."rel="externalnofollow">...</a>
<!--非链接，含有链接冒号-->
<ahref="javascript:void(0)"rel="externalnofollow">javascript:void(0)</a>
<ahref="a:b"rel="externalnofollow">a:b</a>
<ahref="/a#a:b"rel="externalnofollow">/a#a:b</a>
<ahref="mailto:'mafutian@126.com'"rel="externalnofollow">mailto:'mafutian@126.com'</a>
<ahref="/tencent://message/?uin=335134463"rel="externalnofollow">/tencent://message/?uin=335134463</a>
<!--相对路径-->
<ahref="."rel="externalnofollow">.</a>
<ahref=".."rel="externalnofollow">..</a>
<ahref="../"rel="externalnofollow">../</a>
<ahref="/a/b/.."rel="externalnofollow">/a/b/..</a>
<ahref="/a"rel="externalnofollow">/a</a>
<ahref="./b"rel="externalnofollow">./b</a>
<ahref="./././././././././b"rel="externalnofollow">./././././././././b</a><!--其实就是./b-->
<ahref="../c"rel="externalnofollow">../c</a>
<ahref="../../d"rel="externalnofollow">../../d</a>
<ahref="../a/../b/c/../d"rel="externalnofollow">../a/../b/c/../d</a>
<ahref="./../e"rel="externalnofollow">./../e</a>
<ahref="http://www.hole_1.org/./../e"rel="externalnofollow">http://www.hole_1.org/./../e</a>
<ahref="./.././f"rel="externalnofollow">./.././f</a>
<ahref="http://www.hole_1.org/../a/.../../b/c/../d/.."rel="externalnofollow">http://www.hole_1.org/../a/.../../b/c/../d/..</a>
<!--带有端口号-->
<ahref=":8081/index.html"rel="externalnofollow">:8081/index.html</a>
<ahref="http://www.mafutian.net:80/index.html"rel="externalnofollow">:80/index.html</a>
<ahref="http://www.mafutian.net:8081/index.html"rel="externalnofollow">http://www.mafutian.net:8081/index.html</a>
<ahref="http://www.mafutian.net:8082/index.html"rel="externalnofollow">http://www.mafutian.net:8082/index.html</a>

处理的第一步，设置成绝对路径：

http://.../../../

然后本文讲讲如何去除绝对路径中的'./'、'../'、'/..'的实现代码：

functionurl_to_absolute($relative)
{
$absolute='';
//去除所有的'./'
$absolute=preg_replace('/(?<!\.)\.\//','',$relative);
$count=preg_match_all('/(?<!\/)\/([^\/]{1,}?)\/\.\.\//',$absolute,$res);
//迭代去除所有的'/abc/../'
do
{
$absolute=preg_replace('/(?<!\/)\/([^\/]{1,}?)\/\.\.\//','/',$absolute);
$count=preg_match_all('/(?<!\/)\/([^\/]{1,}?)\/\.\.\//',$absolute,$res);
}while($count>=1);
//除去最后的'/..'
$absolute=preg_replace('/(?<!\/)\/([^\/]{1,}?)\/\.\.$/','/',$absolute);
$absolute=preg_replace('/\/\.\.$/','',$absolute);
//除去存在的'../'
$absolute=preg_replace('/(?<!\.)\.\.\//','',$absolute);
return$absolute;
}
$relative='http://www.mytest.org/../a/.../../b/c/../d/..';
var_dump(url_to_absolute($relative));
//输出：string'http://www.mytest.org/a/b/'(length=26)

总结

以上就是这篇文章的全部内容了，希望本文的内容对大家的学习或者工作能带来一定的帮助，如果有疑问大家可以留言交流，谢谢大家对毛票票的支持。

PHP利用正则表达式将相对路径转成绝对路径的方法示例

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