Java – Where is Oracle’s (Sun’s) JDK/JRE installed on Mac OS X 10.8 Mountain Lion

Open a good text editor (I'd recommend TextMate, but the free TextWrangler or vi or nano will do too), and open:

/etc/apache2/httpd.conf

Find the line:

"#LoadModule php5_module        libexec/apache2/libphp5.so"

And uncomment it (remove the #).

Download and install the latest MySQL version from mysql.com. Choose the x86_64 version for Intel (unless your Intel Mac is the original Macbook Pro or Macbook, which are not 64 bit chips. In those cases, use the 32 bit x86 version).

Install all the MySQL components. Using the pref pane, start MySQL.

In the Sharing System Pref, turn on (or if it was already on, turn off/on) Web Sharing.

You should now have Apache/PHP/MySQL running.

In 10.4 and 10.5 it was necessary to modify the php.ini file to point to the correct location of mysql.sock. There are reports that this is fixed in 10.6, but that doesn't appear to be the case for all of us, given some of the comments below.

The JRE is the Java Runtime Environment. It is a package of everything necessary to run a compiled Java program, including the Java Virtual Machine (JVM), the Java Class Library, the java command, and other infrastructure. However, it cannot be used to create new programs.

The JDK is the Java Development Kit, the full-featured SDK for Java. It has everything the JRE has, but also the compiler (javac) and tools (like javadoc and jdb). It is capable of creating and compiling programs.

Usually, if you only care about running Java programs on computer you will only install the JRE. It's all you need. On the other hand, if you are planning to do some Java programming, you need to install the JDK instead.

Sometimes, even if you are not planning to do any Java development on a computer, you still need the JDK installed. For example, if you are deploying a web application with JSP, you are technically just running Java programs inside the application server. Why would you need the JDK then? Because the application server will convert JSP into Java servlets and needs to use the JDK to compile the servlets. I am sure that there are more examples.