Variables are not highlighted inside arrays

[glennsarti]

What Versions are you running?

Editor Name and Version: (If applicable)
Theme: (If applicable)
Document:

$foo = ['bar', $baz, 'wizz']

What You Are Seeing?

$baz is not highlighted

What is Expected?

$baz should be highlighted

How Did You Get This To Happen? (Steps to Reproduce)