PHP利用正则表达式将相对路径转成绝对路径的方法示例

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