Please help me understand the relationship between script file size and memory usage?

Question

I am programming in PHP and I have an include file that I have to, well, include, as part of my script. The include file is 400 MB, and it contains an array of objects which are nothing more than configuration settings for a larger project. Here is an example of the contents:

$obj = new obj();
    $obj->name = "myname";
    ....

$objs[$obj->name] = $obj->name;
{repeat}
....
return $objs;

This process repeats itself 40,000 times and ultimately is 650,000 lines long (the file is generated dynamically of course.)

If I am simply trying to load a file that is 400MB, why then would memory usage increase to 6GB? Even if the file is loaded into memory, wouldn't only take up 400 MB of RAM?