Facebook writes custom PHP JIT Compiler…
This might be my favorite quote from the article about Facebook developing their own version of PHP 
When we asked what he thought of this style of release – years of secretive development by two lonely coders, likely locked in a deep, dark vault – Crowley said it was typical.
“[Facebook] tends to do giant code dumps,” he said. “Facebook tends to build something big, use it, and open source it.”
