minor #1133 Update intro.rst (kix)
minor #1133 Update intro.rst (kix)

This PR was submitted for the master branch but it was merged into the 1.2 branch instead (closes #1133).

Discussion
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Update intro.rst

Added PHP opening tag to make things more clear

Commits
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cce42f5 Update intro.rst

beealone/Silex,lokhman/Silex,romainneutron/Silex,Xephi/Silex,lokhman/Silex,jdreesen/Silex,mTorres/Silex,Incognito/silex-fork,beealone/Silex,fabpot/Silex,fhinkel/Silex,mTorres/Silex,mathroc/Silex,SanderKnape/Silex,gencer/Silex,romainneutron/Silex,plotek/Silex,cgsmith/Silex,mmauri04/Silex,fabpot/Silex,plotek/Silex,Xephi/Silex,SpacePossum/Silex,jdreesen/Silex,SpacePossum/Silex,cesarmarinhorj/Silex,cgsmith/Silex,cesarmarinhorj/Silex,mmauri04/Silex,arduanov/Silex,RayRutjes/Silex,RayRutjes/Silex,Incognito/silex-fork,mathroc/Silex,fhinkel/Silex,SanderKnape/Silex,arduanov/Silex,romainneutron/Silex,silexphp/Silex