Maybe you only think you do. Check out the About menu item. You should see amd64 in the JRE area and 64-Bit in JVM.
The thing is that PhpStorm comes with its own copy of JRE and it will use it unless your environment variables tell it that there’s Java already installed on your system. For full details look into C:\Program Files (x86)\JetBrains\PhpStorm 8.0.1\bin\PhpStorm.bat but what worked for me was simply to set environment variable JAVA_HOME and run PhpStorm64.exe located in the same directory. In my particular case JAVA_HOME=C:\Program Files\Java\jre1.8.0_20.
Tags: PhpStorm 8.0.1