print_r(get_loaded_extensions());

output

======

Array ( [0] => Core [1] => date [2] => ereg [3] => libxml [4] => openssl [5] => pcre [6] => zlib [7] => bcmath [8] => bz2 [9] => calendar [10] => ctype [11] => dba [12] => dom [13] => hash [14] => fileinfo [15] => filter [16] => ftp [17] => gettext [18] => session [19] => iconv [20] => json [21] => mbstring [22] => standard [23] => posix [24] => Reflection [25] => SPL [26] => shmop [27] => SimpleXML [28] => soap [29] => sockets [30] => Phar [31] => exif [32] => sysvmsg [33] => sysvsem [34] => sysvshm [35] => tokenizer [36] => wddx [37] => xml [38] => xmlreader [39] => xmlwriter [40] => zip [41] => apache2handler [42] => curl [43] => gd [44] => mcrypt [45] => mysql [46] => mysqli [47] => PDO [48] => pdo_mysql [49] => mhash )