It's everytime the same game. You compile PHP and you get errors that some packages are not installed. That's OK - the problem is, that on some distros the target package is called differently.

So what about this compilation error, which might appearif you compile PHP with imap support:

checking for IMAP support... yes
checking for IMAP Kerberos support... yes
checking for IMAP SSL support... yes
checking for utf8_mime2text signature... new
checking for U8T_DECOMPOSE...
configure: error: utf8_mime2text() has new signature, but U8T_CANONICAL is missing. This should not happen. Check config.log for additional information.

Unfortunately there is not really an indication which package to install. By using a search engine with the above error message as keywords will give you several pages (e.g. a blog and a php bug) with the following solution:

yum install libc-client-devel

So the missing package seems to be libc-client-devel. But as one can see on the command yum, this ain't Debian. To find the appropriate Debian package, you can launch this command:

# apt-cache search libc-client
libc-client2007b-dev - c-client library for mail protocols - development files
libc-client2007b - c-client library for mail protocols - library files

Seems about right, so let's install them:

# aptitude install libc-client2007b
# aptitude install libc-client2007b-dev

And let's continue with the PHP compilation:

...
checking for IMAP support... yes
checking for IMAP Kerberos support... yes
checking for IMAP SSL support... yes
checking for utf8_mime2text signature... new
checking for U8T_DECOMPOSE...
checking for pam_start in -lpam... yes
checking for crypt in -lcrypt... yes
checking whether build with IMAP works... yes
...

Success!