在RFC 3986中描述了一个Remove Dot Sequence algorithm，用于在相对URI引用解析过程中，从被引用路径中解释和移除特殊的.和..完整路径段。
您也可以将此算法用于文件系统路径：
// as per RFC 3986
// @see https://www.rfc-editor.org/rfc/rfc3986#section-5.2.4
function remove_dot_segments($input) {
// 1. The input buffer is initialized with the now-appended path
// components and the output buffer is initialized to the empty
// string.
$output = '';
// 2. While the input buffer is not empty, loop as follows:
while ($input !== '') {
// A. If the input buffer begins with a prefix of "`../`" or "`./`",
// then remove that prefix from the input buffer; otherwise,
if (
($prefix = substr($input, 0, 3)) == '../' ||
($prefix = substr($input, 0, 2)) == './'
) {
$input = substr($input, strlen($prefix));
} else
// B. if the input buffer begins with a prefix of "`/./`" or "`/.`",
// where "`.`" is a complete path segment, then replace that
// prefix with "`/`" in the input buffer; otherwise,
if (
($prefix = substr($input, 0, 3)) == '/./' ||
($prefix = $input) == '/.'
) {
$input = '/' . substr($input, strlen($prefix));
} else
// C. if the input buffer begins with a prefix of "/../" or "/..",
// where "`..`" is a complete path segment, then replace that
// prefix with "`/`" in the input buffer and remove the last
// segment and its preceding "/" (if any) from the output
// buffer; otherwise,
if (
($prefix = substr($input, 0, 4)) == '/../' ||
($prefix = $input) == '/..'
) {
$input = '/' . substr($input, strlen($prefix));
$output = substr($output, 0, strrpos($output, '/'));
} else
// D. if the input buffer consists only of "." or "..", then remove
// that from the input buffer; otherwise,
if ($input == '.' || $input == '..') {
$input = '';
} else
// E. move the first path segment in the input buffer to the end of
// the output buffer, including the initial "/" character (if
// any) and any subsequent characters up to, but not including,
// the next "/" character or the end of the input buffer.
{
$pos = strpos($input, '/');
if ($pos === 0) $pos = strpos($input, '/', $pos+1);
if ($pos === false) $pos = strlen($input);
$output .= substr($input, 0, $pos);
$input = (string) substr($input, $pos);
}
}
// 3. Finally, the output buffer is returned as the result of remove_dot_segments.
return $output;
}