I agree with Tom. Happy camper using the NetBeans IDE for elgg development; it works like a charme. You need the PHP or complete version, or you install the PHP plug-in, of course.

I use one project for the whole elgg installation with all mods. Deployment is very fast (NetBeans synchronises to the deployment folder as soon as you save a file). What is really time consuming is execution of upgrade.php before changes (esp. css) work. 

Just for my two cents, I use Eclipse + xdebug.  Eclipse has a nice plugin that integrates PHPCodeSniffer so I can easily spot code that's not standardized.

I've never seen that problem before...

Notepad++ here - I have tried other IDE's and editors, but, at least for Windows, nothing feels right except for NP++.

It's simple, loads quickly, and lets me do the work I need to do.

Of course, I have quite a bit of experience in PHP, and would suggest an IDE over NP++ if you aren't too comfortable with PHP.

( Bolded = my Faves )

Eclipse
    XDebug
    PHP addOn ++ other languages && 100's+ supporting tools and utilities
Aptana
    Built on the Eclipse base
NetBeans
    Similar to the above two

NotePad++
    Probably best ever replacement to WiNnoTEePaD
    Interface to XDebug
HtmlKit
    Slick progammer editor, almost a mini IDE
SciTE
    Lean/mean programmer's editor
THE
    Lean/ mean programmer's editor
EMacs/XEMacs
    Lean/mean programmer's editor
EditRocket
    Lean/mean programmer's editor
jEdit
    Lean/mean programmer's editor

I like NotePad++ but DW CS5 has that cool feature of editing any CMS in Design mode.... and it's easy to use.

And for the Eclipse aficionados ->
http://www.eclipse.org/projects/listofprojects.php
;-)

I finally solved the problem!:) thank you all

What was the problem?

I have the same problem that ZunderNet had.
Can you give me the solution please?
Thank you