$ cd /opt/phpfarm/inst/php-5.4.32/etc
$ wget http://pear.php.net/go-pear.phar
$ /opt/phpfarm/inst/php-5.4.32/bin/php ./go-pear.phar
# alegi all
$ /opt/phpfarm/inst/php-5.4.32/pecl -C ./pear.conf update-channels
$ /opt/phpfarm/inst/php-5.4.32/pecl -C ./pear.conf install channel://pecl.php.net/apcu-4.0.6
#
$ vi /opt/phpfarm/inst/php-5.4.32/lib/php.ini

… and add the line extension=apcu.so at the end of the file (you can also configure some additional APCu settings):

[...]
 extension=apcu.so
 apc.enabled=1
 apc.shm_size=128M
 apc.ttl=0
 apc.gc_ttl=600
 apc.enable_cli=1
 apc.mmap_file_mask=/tmp/apc.XXXXXX
 ;apc.mmap_file_mask=/dev/zero
 ;apc.shm_segments = 5

phpinfo():