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PHP利用正則表達式將相對路徑轉(zhuǎn)成絕對路徑的方法示例

 更新時間：2017年02月28日 11:39:11   作者：馬富天  
這篇文章主要介紹了PHP利用正則表達式將相對路徑轉(zhuǎn)成絕對路徑的方法，文中給出了詳細的示例代碼，大家可以整合成一個方法，在需要的地方調(diào)用，非常的不錯。需要的朋友們下面來一起看看吧。

前言

大家應(yīng)該都有所體會，很多時候在做網(wǎng)絡(luò)爬蟲的時候特別需要將爬蟲搜索到的超鏈接進行處理，統(tǒng)一都改成絕對路徑的，所以本文就寫了一個正則表達式來對搜索到的鏈接進行處理。下面話不多說，來看看詳細的介紹吧。

通常我們可能會搜索到如下的鏈接：

<!-- 空超鏈接 -->
<a href=""></a> 
<!-- 空白符 -->
<a href=" " rel="external nofollow" > </a>
<!-- a標(biāo)簽含有其它屬性 -->
<a href="index.html" rel="external nofollow" rel="external nofollow" rel="external nofollow" alt="超鏈接"> index.html </a>
<a href="/" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" target="_blank"> / target="_blank" </a>
<a target="_blank" href="/" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" alt="超鏈接" > target="_blank" / alt="超鏈接" </a>
<a target="_blank" title="超鏈接" href="/" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" alt="超鏈接" > target="_blank" title="超鏈接" / alt="超鏈接" </a>
<!-- 根目錄 -->
<a href="/" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" > / </a>
<a href="a" rel="external nofollow" > a </a>
<!-- 含參數(shù) -->
<a href="/index.html?id=1" rel="external nofollow" > /index.html?id=1 </a>
<a href="?id=2" rel="external nofollow" > ?id=2 </a>
<!-- // -->
<a  rel="external nofollow" > //index.html </a>
<a  rel="external nofollow" > //www.mafutian.net </a>
<!-- 站內(nèi)鏈接 -->
<a  rel="external nofollow" > http://www.hole_1.com/index.html </a>
<!-- 站外鏈接 -->
<a  rel="external nofollow" > http://www.mafutian.net </a>
<a  rel="external nofollow" > http://www.numberer.net </a>
<!-- 圖片，文本文件格式的鏈接 -->
<a href="1.jpg" rel="external nofollow" > 1.jpg </a>
<a href="1.jpeg" rel="external nofollow" > 1.jpeg </a>
<a href="1.gif" rel="external nofollow" > 1.gif </a>
<a href="1.png" rel="external nofollow" > 1.png </a>
<a href="1.txt" rel="external nofollow" > 1.txt </a>
<!-- 普通鏈接 -->
<a href="index.html" rel="external nofollow" rel="external nofollow" rel="external nofollow" > index.html </a>
<a href="index.html" rel="external nofollow" rel="external nofollow" rel="external nofollow" > index.html </a>
<a href="./index.html" rel="external nofollow" > ./index.html </a>
<a href="../index.html" rel="external nofollow" > ../index.html </a>
<a href=".../" rel="external nofollow" > .../ </a>
<a href="..." rel="external nofollow" > ... </a>
<!-- 非鏈接，含有鏈接冒號 --> 
<a href="javascript:void(0)" rel="external nofollow" > javascript:void(0) </a>
<a href="a:b" rel="external nofollow" > a:b </a>
<a href="/a#a:b" rel="external nofollow" > /a#a:b </a>
<a href="mailto:'mafutian@126.com'" rel="external nofollow" > mailto:'mafutian@126.com' </a>
<a href="/tencent://message/?uin=335134463" rel="external nofollow" > /tencent://message/?uin=335134463 </a> 
<!-- 相對路徑 -->
<a href="." rel="external nofollow" > . </a>
<a href=".." rel="external nofollow" > .. </a>
<a href="../" rel="external nofollow" > ../ </a>
<a href="/a/b/.." rel="external nofollow" > /a/b/.. </a>
<a href="/a" rel="external nofollow" > /a </a>
<a href="./b" rel="external nofollow" > ./b </a>
<a href="./././././././././b" rel="external nofollow" > ./././././././././b </a> <!-- 其實就是 ./b -->
<a href="../c" rel="external nofollow" > ../c </a>
<a href="../../d" rel="external nofollow" > ../../d </a>
<a href="../a/../b/c/../d" rel="external nofollow" > ../a/../b/c/../d </a>
<a href="./../e" rel="external nofollow" > ./../e </a>
<a  rel="external nofollow" > http://www.hole_1.org/./../e </a> 
<a href="./.././f" rel="external nofollow" > ./.././f </a>
<a  rel="external nofollow" > http://www.hole_1.org/../a/.../../b/c/../d/.. </a> 
<!-- 帶有端口號 -->
<a href=":8081/index.html" rel="external nofollow" > :8081/index.html </a>
<a  rel="external nofollow" > :80/index.html </a>
<a  rel="external nofollow" > http://www.mafutian.net:8081/index.html </a>
<a  rel="external nofollow" > http://www.mafutian.net:8082/index.html </a>

處理的第一步，設(shè)置成絕對路徑：

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

然后本文講講如何去除絕對路徑中的 './'、'../'、'/..'的實現(xiàn)代碼：

function url_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));
// 輸出：string 'http://www.mytest.org/a/b/' (length=26)

總結(jié)

以上就是這篇文章的全部內(nèi)容了，希望本文的內(nèi)容對大家的學(xué)習(xí)或者工作能帶來一定的幫助，如果有疑問大家可以留言交流，謝謝大家對腳本之家的支持。

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