adjusting wp-config.php for multisite

This should be so easy, but when I add the line to allow for multisite (and I did check that the ' is correct) and save as a .php, when I upload it to the site, it changes the file size from 3416 to 3324. When I send it back to see what it looks like/changes it made, the code comes in as one or two lines instead of 100 or so separate lines. Do you know what's causing this? This simple change keeps wiping out my dashboard. Thanks!