#Reemplaza <?=
find . -type f -name "*.php" | xargs perl -pi -e 's/<\?=/<\?php echo /g';
#Reemplaza <? 
find . -type f -name "*.php" | xargs perl -pi -e 's/<\?[\s]*$/<\?php\n/g';
#Reemplaza <? echo
find . -type f -name "*.php" | xargs perl -pi -e 's/<\? echo/<\?php echo/g';