PHP: 6,883,004 Domains, 976,593 IP Addresses
Source: Netcraft
The drop-off in August is related to the .com crash with a number of sites and ISP's disappearing. Netcraft's total number of sites found dropped in August from 31,299,592 to 30,775,624. PHP's percentage actually rose from 22.2% to 22.4%
You can also see how popular PHP is relative to other Apache modules at . Spoiler: PHP is the most popular.