Better yet:
$ php --ini
This will also show all extra *.ini files loaded (usually hanging around in some conf.d dir in debian):
Configuration File (php.ini) Path: /etc/php5/cli
Loaded Configuration File: /etc/php5/cli/php.ini
Scan for additional .ini files in: /etc/php5/cli/conf.d
Additional .ini files parsed: /etc/php5/cli/conf.d/apc.ini,
/etc/php5/cli/conf.d/curl.ini,
/etc/php5/cli/conf.d/gd.ini,
/etc/php5/cli/conf.d/geoip.ini,
/etc/php5/cli/conf.d/imagick.ini,
/etc/php5/cli/conf.d/imap.ini,
/etc/php5/cli/conf.d/ldap.ini,
/etc/php5/cli/conf.d/memcache.ini,
/etc/php5/cli/conf.d/memcached.ini,
/etc/php5/cli/conf.d/ming.ini,
/etc/php5/cli/conf.d/mysql.ini,
/etc/php5/cli/conf.d/mysqli.ini,
/etc/php5/cli/conf.d/pdo.ini,
/etc/php5/cli/conf.d/pdo_mysql.ini,
/etc/php5/cli/conf.d/pdo_sqlite.ini,
/etc/php5/cli/conf.d/snmp.ini,
/etc/php5/cli/conf.d/sqlite.ini,
/etc/php5/cli/conf.d/sqlite3.ini,
/etc/php5/cli/conf.d/suhosin.ini,
/etc/php5/cli/conf.d/tidy.ini,
/etc/php5/cli/conf.d/xdebug.ini,
/etc/php5/cli/conf.d/xsl.ini
Note that this was about php-cli, php-cgi does not have this afaik.