Adjust PHP indentation defaults to 4 spaces

In the PHP community, 4 spaces is widely considered the default, as
it is recommended by the PSR-2 and PSR-12 standards, as well as popular
derivative standards like those for Laravel and Symphony.

languages.toml

@@ -200,7 +200,7 @@ injection-regex = "php"
 file-types = ["php"]
 roots = []
 
-indent = { tab-width = 2, unit = "  " }
+indent = { tab-width = 4, unit = "    " }
 
 [[language]]
 name = "latex"