how to search for a file with php

$file_to_search = "abc.pdf";

search_file('.',$file_to_search);




function search_file($dir,$file_to_search){

$files = scandir($dir);

foreach($files as $key => $value){

    $path = realpath($dir.DIRECTORY_SEPARATOR.$value);

    if(!is_dir($path)) {

        if($file_to_search == $value){
            echo "file found<br>";
            echo $path;
            break;
        }

    } else if($value != "." && $value != "..") {

        search_file($path, $file_to_search);

    }  
 } 
}

class Test
{
    public static function find($dir, $targetFile)
    {
        $filePath = null;

        // pass function ref &$search so we can make recursive call
        // pass &$filePath ref so we can get rid of it as class param
        $search = function ($dir, $targetFile) use (&$search, &$filePath) {
            if (null !== $filePath) return; // early termination
            $files = scandir($dir);
            foreach ($files as $key => $file) {
                if ($file == "." || $file == "..") continue;
                $path = realpath($dir . DIRECTORY_SEPARATOR . $file);
                if (is_file($path)) {
                    if ($file === $targetFile) {
                        $filePath = $path;
                        break;
                    }
                } else {
                    $search($path, $targetFile);
                }
            }
        };

        $search($dir, $targetFile); // invoke the function

        return $filePath;
    }
}

// $dir = './', $targetFile = "Foo.php";
echo Test::find($dir, $targetFile);