Fix the PHP language

[zeitgeist87]

This patch is an attempt to fix the PHP language, when it is combined
with markup.

The problem is, that markup has a higher priority than all other tokens.
This leads to weird errors, where HTML tags are highlighted inside of
comments #197. One solution to this was to set the greedy flag for the
comment token, but this leads to far worse errors like #1097.

This patch should fix both issues #197 and #1097, by switching the
grammar to markup on the fly. One potential problem is, that it relies
on the <?php tag to detect if markup is present. So if a PHP file
contains only markup and no PHP code at all, the result will look
broken.

[zeitgeist87]

Before (Note: The JavaScript function is erroneously highlighted by PHP. CSS is not highlighted at all. Strings inside comments do not work):

After (Note: The string "px" looks different, because CSS has custom styles for the class token string. JavaScript and CSS are highlighted by the correct language.) :

[zeitgeist87]

There is one problem with this PR. If there are no <?php tags, then it assumes, that it is pure PHP code, which could be wrong:

If a <?php tag is present, then markup is also highlighted:

[zeitgeist87]

@LeaVerou @Golmote What do you think about this PR?

[LeaVerou]

If there are no <?php tags, then it assumes, that it is pure PHP code, which could be wrong:

I don't think that's a huge problem (they can use markup in those cases), as long as it supports the shortened PHP tags as well (<?= etc). Though I don't see why we can't check if a PHP tag is present and use the markup definition if not.

[zeitgeist87]

Though I don't see why we can't check if a PHP tag is present and use the markup definition if not.

Yes that is one option, but I think it is more intuitive to assume that it is all PHP in that case. For example someone could use small snippets of PHP code between paragraphs on a blog to explain a larger file:

$test = "<div>" . $_SERVER['PHP_SELF'] . "</div>";

If we switch to markup in that scenario, we would force the users to put PHP tags around every small snippet:

<?php $test = "<div>" . $_SERVER['PHP_SELF'] . "</div>"; ?>

If there is no PHP code at all, people should use markup directly.

[LeaVerou]

Ah yeah, excellent point! Completely agree.

[Golmote]

@zeitgeist87 Sorry for the looong time before review. This looks ok to me! ;) Feel free to merge.

[zeitgeist87]

@Golmote Thanks again for the review! Merging...