laravel/docs — pull request #873 by Bux666 (2014-07-28 07:56:57+00:00)
Title: Update schema.md

Added 2 pieces of extra info to the Foreign Keys part:
1. $table->integer('user_id')->unsigned();
2. Make sure to create the foreign key column first.

This should make clear that you can't make a foreign key without the foreign key column.