app/code/community/Aoe/TemplateHints/Helper/ClassInfo.php
public function searchFullPath($filename) {
        $paths = explode(PATH_SEPARATOR, get_include_path());
        foreach ($paths as $path) {
            $fullPath = $path . DIRECTORY_SEPARATOR . $filename;
            if (file_exists($fullPath)) {
                return $fullPath;
            }
        }
        return false;
    }
public function searchFullPath($filename) {
        $paths = explode(PATH_SEPARATOR, get_include_path());
        foreach ($paths as $path) {
            $fullPath = $path . DIRECTORY_SEPARATOR . $filename;
            if (file_exists($fullPath)) {
                return $fullPath;
            }
        }
        return false;
    }
Find a filename in the include path fallback

@param $filename
@return bool|string