filepath.md

OK, so you have a filepath made from user input; something like

$path = __DIR__ . "/uploads/{$user_input_filename}"

#1: DO NOT DO THIS. Make up your own directory names. The user has no business picking path names on your server.

#2: Filesystem traversal is bad. If you mean for the given $user_input_filename to be inside the __DIR__ . "/uploads/ directory, take a moment to check.

<?php

$target_dir = realpath(__DIR__ . '/uploads');
$full_path = "{$target_dir}/{$user_input_filename}";
if ($full_path !== realpath($full_path)) {
    /* not a real file, or a relative path that doesn't go where you expect. bad! */
}

#3: see #1