Here is what I do:

When a huge amount of code is due to be selected I do what every Windows user usually does: first select small piece of text, than go with scroll/wheel down to end of select (not holding mouse button any more), hold SHIFT and click on point where end of selection should be.

Everything is selected, BUT first selection ie PhpEd will not add new selection to old one. Instead it will select from last caret position to new end point.

Now this cause me major frustration more than one time, until I figure out how to select text in PhpEd, but it wouldn't hurt to maintain same way of doing things in all Windows apps.

Can you do something about this?

Agreed, phped behaves differently than expected in that situation.
Shift + Click on an existing selection usually extends the selection in most windows programs I know of.

In most programs: If you click behind the selection it gets extended, if you click before it the piece from the initial cursor position to your click position is selected, unless you started out by selecting in the other direction, in which case everything reverses.

Personally all that mouse stuff doesn't bother me since I pretty much use the keyboard only, but that doesn't mean I didn't notice it

Probably you didn't try version 5.6. What you described works in this version the way you expected it to work.
Indeed, if you select small piece of code by dragging mouse toward the end of file with Left button held down, then scroll toward the end of file and Shift-Click, it will select everything.
You may want to try NotePad and it works the same way.

No it doesn't
I've tried it before I posted here and it works as konixmet described.
If you have an existing selection, either with mouse or keyboard and you shift click further along the file, the existing selection will be gone and the piece from the end of the previous selection till the place where you clicked will now be selected. Perhaps this is an option that you can toggle and that I missed, but the IDE behaves differently than what you just described here.

Version is 5618 and I think that's the latest.

To recap:

- set caret at beginning of selection ad drag with mouse small portion (select it)
- depress mouse button
- hold SHIFT and click with mouse on new end point

New selection is made from last end caret position to new end. This is not good.
Selection should be made from original beginning to new end.

Btw Notepad/Wordpad/Word does it exactly like I described. The right way

don't start with multiple lines selected. Just one-two words. Then Shift-Click on the point below and you'll see it works.

True dimitri, but it doesn't solve the problem quite right, does it