syntax: php: colorize the full short tag for echo (<?=)

syntax/php.nanorc

@@ -5,7 +5,7 @@ magic "PHP script"
 comment "//"
 
 # PHP markings.
-color brightgreen "(<\?(php)?|\?>)"
+color brightgreen "(<\?(php|=)?|\?>)"
 
 # Function names.
 color white "\<[A-Za-z_][A-Za-z_0-9]*\("