get in a bash shell:

php -m; # list all currently activated and installed extensions
[PHP Modules]
bcmath
bz2
calendar
Core
ctype
curl
date
dba
dom
ereg
exif
fileinfo
filter
ftp
gd
gettext
hash
iconv
imap
intl
json
libxml
mbstring
mcrypt
mhash
mysql
mysqli
openssl
pcntl
pcre
PDO
pdo_mysql
pdo_sqlite
Phar
posix
pspell
recode
Reflection
session
shmop
SimpleXML
snmp
soap
sockets
SPL
sqlite3
standard
sysvmsg
sysvsem
sysvshm
tidy
tokenizer
wddx
xdebug
xml
xmlreader
xmlrpc
xmlwriter
xsl
zip
zlib

[Zend Modules]
Xdebug

admin