Search through a directory in PHP, beginning at the end [duplicate] - php

Question

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How to use return inside a recursive function in PHP
(4 answers)
Closed 9 months ago.
I have this PHP code, but I have only written one recursive function before. I want to begin in a particular subdirectory and check for the presence of a file. If it doesn't exist in the directory I want to check the parent folder for the file and then recursively go on until I either don't find the file and return "" or find the file and return its contents. Here is my function:
/**
* Recursive function to get sidebar from path and look up tree until we either
* find it or return blank.
*/
class MyClass{
public function findSidebarFromPath($path){
if(file_exists($_SERVER["DOCUMENT_ROOT"] . implode("/", $path) . "/sidebar.html")){
return file_get_contents($_SERVER["DOCUMENT_ROOT"] . implode("/", $path) . "/sidebar.html");
} else {
if(count($path) > 0){
# Pop element off end of array.
$discard = array_pop($path);
$this->findSidebarFromPath($path);
} else {
return "";
}
}
}
}
So when I call it, I do this:
$myclass = new MyClass();
$myclass->findSidebarFromPath(array("segment1", "segment2", "segment3"));
Let's say the file I am trying to find is in a directory called "segment2". The function never finds it. The array_pop function doesn't pop off the element off the end of the array and then call the findSidebarFromPath function.

Answer 1

If you write this as a standalone function, it will probably be more useful to you in other areas. After we understand how it works, we'll show you how you can add a public function to your class that can utilize it.
/**
* #param $root string - the shallowest path to search in
* #param $path string - the deepest path to search; this gets appended to $root
* #param $filename string - the file to search for
* #return mixed - string file contents or false if no file is found
*/
function findFile($root, $path, $filename) {
// create auxiliary function that takes args in format we want
$findFileAux = function($cwd, $filename) use (&$findFileAux, $root) {
// resolve the complete filename
$file = "{$cwd}/{$filename}";
// if the file exists, return the contents
if (file_exists($file)) return file_get_contents($file);
// if the cwd has already reached the root, do not go up a directory; return false instead
if ($cwd === $root) return false;
// otherwise check the above directory
return $findFileAux(dirname($cwd), $filename);
};
// starting checking for the file at the deepest segment
return $findFileAux("{$root}/{$path}", $filename);
}
Check the example output on ideone.
So here's how to use it
findFile($_SERVER["DOCUMENT_ROOT"], "foo/bar/qux", "sidebar.html");
Here's how you would integrate it with your class. Notice that this public function has the same API as in your original code
class MyClass {
/**
* #param $path array - path segments to search in
* #return mixed - string file contents or false if sidebar is not found
*/
public function findSidebarFromPath($path) {
// Here we call upon the function we wrote above
// making sure to `join` the path segments into a string
return findFile($_SERVER["DOCUMENT_ROOT"], join("/", $path), "sidebar.html";
}
}
Additional explanation
If $_SERVER["DOCUMENT_ROOT"] is /var/www...
Check /var/www/foo/bar/qux/sidebar.html, return if exists
Check /var/www/foo/bar/sidebar.html, return if exists
Check /var/www/foo/sidebar.html, return if exists
Check /var/www/sidebar.html, return if exists
Because we got to the root (/var/www) no further searches will happen
return false if sidebar.html did not exist in any of the above
Here's the same function with the explanatory comments removed
/**
* #param $root string - the shallowest path to search in
* #param $path string - the deepest path to search; this gets appended to $root
* #param $filename string - the file to search for
* #return mixed - string file contents or false if no file is found
*/
function findFile($root, $path, $filename) {
$findFileAux = function($cwd, $filename) use (&$findFileAux, $root) {
$file = "{$cwd}/{$filename}";
if (file_exists($file)) return file_get_contents($file);
if ($cwd === $root) return false;
return $findFileAux(dirname($cwd), $filename);
};
return $findFileAux("{$root}/{$path}", $filename);
}
You might also want to consider using DIRECTORY_SEPARATOR instead of the hard-coded "/" so that this code could be used reliably on a variety of platforms.