How to reliably resolve a path relative to another?

Asked Aug 01 '19 at 11:33

Active Aug 01 '19 at 11:33

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In PHP, is there a built-in way to resolve a path relative to another?

For example, given a $baseDir dir: /home/ben/project, the following $path should resolve to:

/foo/bar → /foo/bar
../foo/bar, → /home/ben/foo/bar

Solutions that come to mind:

Temporarily changing the current working directory, and using realpath():

$currentDir = getcwd();
chdir($baseDir);
$resolvedPath = realpath($path);
chdir($currentDir);

return $resolvedPath;

This solution is a bit tedious.

Checking if the path is absolute, if not, using realpath():
```
if ($path[0] === '/') {
    return $path;
}

return realpath($currentDir . '/' . $path);
```
This solution is not cross-platform; making it safely cross-platform may not be as trivial as it looks.

Last but not least, realpath() returns false when the path does not exist, which is not taken into account in the above codes, and may be a problem in some use cases.

Did I miss something?

asked Aug 01 '19 at 11:33

BenMorel

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why you think your second solution is not cross-platform? – Giacomo M Aug 01 '19 at 11:37
@GiacomoM Because on Windows, paths may start with `C:\ `, not `/`. And I'm not sure about other OSes. – BenMorel Aug 01 '19 at 12:07
PHP does have a constant DIRECTORY_SEPARATOR that is cross-platform – Giacomo M Aug 01 '19 at 12:10
The directory separator is not the problem, `/` does work on Windows, too. The problem is reliably checking if a path is absolute or relative. – BenMorel Aug 01 '19 at 12:12
Still do not understand why you think is not cross-platform – Giacomo M Aug 01 '19 at 12:13
To check if path is absolute or relative check this post https://stackoverflow.com/questions/7392274/checking-for-relative-vs-absolute-paths-urls-in-php – Giacomo M Aug 01 '19 at 12:21

How to reliably resolve a path relative to another?

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