There are several editors out there with support for CHM integration, but you may need to know a few things about what the CHM contains to successfully integrate the manual into your environment.
The CHM is built using XSL style sheets from XML sources. This is unique currently in the PHP Manual family, as all other versions are generated using DSSSL style sheets. This also means, that non-intentional rendering differences may come up. A special conversion script is run on the XSLT output, adding several cute features, and packing up the manual with the preferences files and skin examples.
If you never worked with CHMs, you can think of them as compressed files with OS supported access for files inside and some added search and index support. However CHMs can only be viewed using the HTML Help Viewer, you can directly access files inside them using a special URL prefix, the CHM file name and the file you request from inside. As all the help content is stored in HTML files, you can show pages of the CHM in Internet Explorer.
Assume that you placed your php_manual_en.chm to c:\phpmanual the index file in the manual (which you see the first time) can be accessed with the following URL: mk:@MSITStore:C:\phpmanual\php_manual_en.chm::/_index.html. Here mk:@MSITStore: is the special "protocol", C:\phpmanual\php_manual_en.chm is the CHM with it's full path. The /_index.html part is the path to the index file inside the CHM and :: is just what you need to put between the CHM path and this file path.
The names of generated files follow the same rules as the online manual, except that the extension is .html and not .php. The most important is that function documentation files are named function.FUNCNAME.html where FUNCNAME is the function name, with all underscores converted to hyphens. Some examples are function.echo.html, function.mysql-close.html, function.imagecopy.html.
Using all this information, you can show a manual page for a function requested by a user. A simple example is included in the distribution, named php_quickref.hta. This is a HTML Application to demonstrate the simple process of showing a manual page for a function. The quickRef() function defined therein does the job.
If you would like to integrate the manual into an IDE without direct support for the PHP manual (actually the underscore to hyphen conversion), you can use the included _function.html file to access a function page. This file is simply a redirector, and can be parameterized via the URL, as _function.html#mysql_close. This page will redirect you to the mysql_close function page (function.mysql-close.html) automatically. You can provide the full path of this file if your IDE supports context sensitive help, and provide the IDE specified string as the parameter. An example for this is the UltraEdit 9 intergation (see the edition's website).
The index of the manual (accessible via the index tab on the navigation pane) can also be used for integrational purposes. All the HTML pages are included in the index with their titles as index terms (including function description pages).
If you are a desktop application developer and would like to tightly integrate the CHM into your program (such as displaying the TOC tree in your IDE's help box), you can find more information at http://www.helpware.net/, as well as links to other useful resources. The official site for HTML Help is at http://msdn.microsoft.com/library/en-us/htmlhelp/html/vsconhh1start.asp.