php-getRelativePath PHP计算文件的相对路径

在程序中经常会用到相对路径，这里写个函数。
[关键词] parse_url

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function abpath($a, $b) {

    $ainfo = parse_url($a);

    $binfo = parse_url($b);
    $apath = ltrim($ainfo['path'], '/');
    $bpath = ltrim($binfo['path'], '/');

    $arr = explode('/',$apath);
    $brr = explode('/',$bpath);

    foreach ($arr as $key=>$value) {
        if($value==$brr[$key]) {
            $brr[$key] = '..';
        }
    }
    $cha = implode('/',$brr);
    return $cha;
}

计算文件$b相对于文件$a的路径，如
$a = ’/a/b/c/d/e.php’; $b = ’/a/b/12/34/c.php’;

结果
../../12/34/c.php

下面是关于parse_url的用法

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$url = 'http://username:password@hostname/path?arg=value#anchor';

print_r(parse_url($url));

echo parse_url($url, PHP_URL_PATH);

以上例程会输出：

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Array
(
    [scheme] => http
    [host] => hostname
    [user] => username
    [pass] => password
    [path] => /path
    [query] => arg=value
    [fragment] => anchor
)

/path