Phpinfo() and Global Vars

[Jawelin]

How could I read all (each one) the vars displayed in phpinfo() ?
I found somewhere the reference to one or another .... but can't understand the exact difference between global var series.
Most of all, where find a complete reference of each global var accessible via PHP code (and hopefully echoable ... leased: ) Could I even redirect the output of phpinfo(parameter), for example ?

Note: I've already checked the PHP Manual: Predefined variables page, but it isn't complete, as itself said

Note: This list is neither exhaustive nor intended to be. It is simply a guideline as to what sorts of predefined variables you can expect to have access to in your script.

Even I got almost confused by the VBulletin management of those vars. Sometimes some are accessed by getenv() function, sometimes directly via a $HTTP_var constant.
What's the difference ???

Thanks

Bye