This blog-post might interest you : Pear: “go-pear.phar” Does Not Have a Signature

It explains how to change a configuration option in php.ini to avoid this error message, and what s said it for WAMP 2.0 and PHP 5.3, so might work in your case.

Just in case anyone comes here from Google: We fixed the .phar download yesterday on http://pear.php.net/go-pear.phar.

In some circumstances (well, actually only on Windows :-)) the file could corrupt from the download. So for example, a lot of people wanted to download it and ended up copy-pasting the contents, etc..

We ve asked some people on Windows to test and so far it worked for everyone I talked to. Let me know if it works for you.

Let’s try this from the PEAR directory. cd PEAR and let’s try that again.

php.exe -d phar.require_hash=0 go-pear.phar

Now the PEAR install runs fine.

If the go-pear.bat file won t run, try this procedure:

1. issue this command with cmd.exe:

   php -d phar.require_hash=0 go-pear.phar 
   

   Allow the installer to edit php.ini.

2. Check the contents of PEAR_ENV.reg - located in the PEAR directory YOUR-PHP-INSTALL-PATHPEAR folder (ex. c:PHPPEARPEAR_ENV.reg) to be sure it has the paths right. Edit as needed and run it. Check your path and environment variables for correctness, then do the same in go-pear.bat and php.ini (mine needed to be corrected to point correctly to my php.exe file).

3. Issue the

   pear
   

   command at the command line to test the path configuration. It will run and do everything but still can t install packages due to a missing dependency.

4. Download and uncompress Structures_Graph from the PEAR website (direct link).The file has three folders - docs, Structures and tests. Copy the Structure folder into the YOUR-PHP-INSTALL-PATHPEAR folder (ex. c:PHPPEARStructures).

5. Issue the command:

   pear install Structures_Graph
   

   Even though the files are present, Structures_Graph is not really installed unless you issue the above command.

6. Issue the command:

   pear update PEAR

7. Enjoy!

   Good luck and thanks to Marcos Roriz for the graph dependency half of my solution!