XAMPP won't start Apache on Mac OS X 10.10.3 Yosemite

After months of trying, I finally got it working. I found the solution here: disable OSX's built-in Apache server.

sudo launchctl unload -w /System/Library/LaunchDaemons/org.apache.httpd.plist

You should check for other processes bound on a TCP socket to port 80.

netstat -atp tcp | grep -i "listen"

Achive Internet connections (including servers)
Proto Recv-Q Send-Q  Local Address          Foreign Address        (state)   
tcp4       0      0  localhost.25035        *.*                    LISTEN

sudo lsof -i -P | grep -i "listen"

COMMAND     PID      USER   FD   TYPE             DEVICE SIZE/OFF NODE NAME
GitHub      850 grgarside   6u   IPv4 0x23c345381d089301      0t0  TCP localhost:25035 (LISTEN)