The image show that a textarea tag with the default message being a <?php ?> tag doesn’t get highlighted.
Notice that if a space is put between the ‘>’ and ‘<’ the highlight works, but you get two extra spaces in your textarea (which is not a valid solution).
I suppose that the problem is the question mark on the php tag, but I can’t guarantee it.
The line 14 and 16 show the expected behavior, but line 15 shows everything white/gray. Even the closing textarea tag.