PHP: 6,624,340 Domains, 979,572 IP Addresses
Source: Netcraft
There have been some shakeout in the large-scale shared hosting space related to the .com crash and combine with some routing issues in Germany which caused 5-10% of German servers not being able to respond to the Netcraft queries. This hurt the PHP total domain numbers a bit, but the number of unique ips seen running PHP is still up.
You can also see how popular PHP is relative to other Apache modules at . Spoiler: PHP is the most popular.