As detailed in T141723#5057472, `mb_strtoupper`, which we use to normalise titles, changes slightly in PHP7 with the Unicode update. As a result certain titles will have their normalised forms changed, and therefore will be unreachable if nothing is changed,
for example https://en.wikipedia.org/w/index.php?title=%C7%85&redirect=no takes you to article ID 7074938 in PHP5, but if you enable the PHP7 beta feature, it takes you to 7074928, and the old article is now completely inaccessible.
Here are the changes (removed lines means the right hand side is no longer the result of mb_strtoupper, added lines are where the right hand side is a new result of mb_strtoupper):
```lang=diff
--- a/resources/src/mediawiki.Title/phpCharToUpper.js
+++ b/resources/src/mediawiki.Title/phpCharToUpper.js
@@ -6,15 +6,8 @@
var toUpperMapping = {
'ß': 'ß',
'ʼn': 'ʼn',
- 'Dž': 'Dž',
- 'dž': 'Dž',
- 'Lj': 'Lj',
- 'lj': 'Lj',
- 'Nj': 'Nj',
- 'nj': 'Nj',
'ǰ': 'ǰ',
- 'Dz': 'Dz',
- 'dz': 'Dz',
+ 'ɪ': 'Ɪ',
'ʝ': 'Ʝ',
'ͅ': 'ͅ',
'ΐ': 'ΐ',
@@ -26,6 +19,15 @@
'ᏻ': 'Ᏻ',
'ᏼ': 'Ᏼ',
'ᏽ': 'Ᏽ',
+ 'ᲀ': 'В',
+ 'ᲁ': 'Д',
+ 'ᲂ': 'О',
+ 'ᲃ': 'С',
+ 'ᲄ': 'Т',
+ 'ᲅ': 'Т',
+ 'ᲆ': 'Ъ',
+ 'ᲇ': 'Ѣ',
+ 'ᲈ': 'Ꙋ',
'ẖ': 'ẖ',
'ẗ': 'ẗ',
'ẘ': 'ẘ',
```