gistfile1.txt

noname@debian6-64:/tmp/hoge$ sudo aptitude install php5-memcached
The following NEW packages will be installed:
  php5-memcached{b}
0 packages upgraded, 1 newly installed, 0 to remove and 0 not upgraded.
Need to get 34.8 kB of archives. After unpacking 119 kB will be used.
The following packages have unmet dependencies:
  php5-memcached: Depends: libmemcached10 which is a virtual package.
The following actions will resolve these dependencies:

     Keep the following packages at their current version:
1)     php5-memcached [Not Installed]



Accept this solution? [Y/n/q/?] n
The following actions will resolve these dependencies:

     Remove the following packages:
1)     libapache2-mod-php5
2)     php5-cli

     Install the following packages:
3)     libmemcached5 [0.40-1 (stable)]
4)     php5-cgi [5.3.3-7+squeeze14 (stable)]
5)     php5-memcached [1.0.2-1+squeeze2 (stable)]
6)     php5-suhosin [0.9.32.1-1 (stable)]

     Downgrade the following packages:
7)     php5 [5.4.12-1~dotdeb.1 (now, stable) -> 5.3.3-7+squeeze14 (stable)]
8)     php5-common [5.4.12-1~dotdeb.1 (now, stable) -> 5.3.3-7+squeeze14 (stable)]



Accept this solution? [Y/n/q/?] q
Abandoning all efforts to resolve these dependencies.
Abort.
-------
noname@debian6-64:/tmp/hoge$ apt-get source php5-memcached
Reading package lists... Done
Building dependency tree
Reading state information... Done
Skipping already downloaded file 'php-memcached_1.0.2-1+squeeze2.dsc'
Skipping already downloaded file 'php-memcached_1.0.2.orig.tar.gz'
Skipping already downloaded file 'php-memcached_1.0.2-1+squeeze2.debian.tar.gz'
Need to get 0 B of source archives.
Skipping unpack of already unpacked source in php-memcached-1.0.2

http://packages.dotdeb.org/dists/squeeze-php54/php5-pecl/
no source directory

Be sure to have this line in your sources.list :

deb http://packages.dotdeb.org squeeze all

It brings the libmemcached10 dependency : http://packages.dotdeb.org/dists/squeeze/libmemcached/binary-amd64/

FYI, PECL packages are built this way : http://www.dotdeb.org/2008/09/25/how-to-package-php-extensions-by-yourself/