PHP version 1, by Rasmus Lerdorf, was released into the world on June 8, 1995. It’s original name of Personal Home Page was renamed, with a heavy nod to recursion, to “PHP: Hypertext Preprocessor” in 1998 with the launch of version 3.

I owe a great deal of my professional success to this language, it is the one that truly sold me on programming.
<?php
/**
* June 9, 2010
*/
echo<<<HAPPY15THBIRTHDAYPHP
* May your future be full of fantastic features and ever greater efficiencies.
* You've powered the dynamic web from yahoo to facebook.
* May you continue to enthrall and encourage programmers young and old.
* You've come a long way, be sure to have lots and lots of cake today.
* May your full fledged Unicode support be your gift to us sooner rather than later.
* You've got your problems, but then don't we all.
* May you survive and thrive another 15 years.
HAPPY15THBIRTHDAYPHP;
?>
Bonus: here’s some cool PHP usage statistics and trend graphs.