I have been using Apache and PHP together with mySQL for a long time. I just came across the following resources and got a brief idea about how popular they might be among other developers.
PHP:
php is one of the most popular interpreted programming languages of today. PHP was created as a Personal Home Page (php) tool by Rasmus for maintaining his personal web site. But the ease and flexibility of the language has won the hearts of millions. Now php is perhaps the most widely used language for web scripting.
Visit this link: http://www.php.net/usage.php to see a graph illustrating the popularity of php. The graph shows the continual increment in the usage of php over the years.
Apache:
The most popular web server of the present day. The following link shows you a graph from the web server survey conducted by netcraft in March, 2009.
Link: http://news.netcraft.com/archives/2009/03/15/march_2009_web_server_survey.html
From the report, it is seen that 66.65% web servers run on Apache.
From the stats it is clear that Apache being free and open sourced, holds the largest share in the web server market. Though the php related chart doesn’t show relative comparison of php with other languages, I wonder if any other languages are used as widely as php is.