Unexpected 'use' (T_USE) error when using autoload

Question

I have the following folder and file structure:

-api
  -v1
  -libs
    -Slim
    -Facebook
      -autoload.php
  -index.php
  -login.php

Inside the "index.php" I do the include of "login.php":

require_once 'login.php';

Inside "login.php" I do the include of the file "libs/Facebook/autoload.php" and then try to use a class:

require_once 'libs/Facebook/autoload.php';
use Facebook\FacebookSession;

The following error is returned:

Parse error: syntax error, Unexpected 'use' (T_USE)

"autoload.php" contains the following code:

spl_autoload_register(function ($class){
   $prefix = 'Facebook\\';
   $base_dir = __DIR__;
   $len = strlen($prefix);
   if (strncmp($prefix, $class, $len) !== 0) {
      return;
   }
   $relative_class = substr($class, $len);
   $file = $base_dir . str_replace('\\', '/', $relative_class) . '.php';
   if (file_exists($file)) {
      require $file;
   }
});

What I’m doing wrong so the autoload doesn’t work properly?

Answer 1

As this response from Soen:

This is because you probably set the namespace within a method or function, read on PHP: Using Namespaces:

The use must be declared in the outermost scope of a file (in global reach) or within declarations namespace. This is because the import is done at compile time and not run time, so it cannot be block scope.

To resolve you must move the use out of any function or class.

Supposing you’re like this:

function initiate () {
    require_once 'libs/Facebook/autoload.php';
    use Facebook\FacebookSession;
    ...
}

Do this:

require_once 'libs/Facebook/autoload.php';
use Facebook\FacebookSession;

function initiate () {
    ...
}