Hi,
in MW 1.31.1, PHP 7.1.22 and TitelIcon 4, I get the follwing error:
... Error from line 289 of .../extensions/TitleIcon/TitleIcon.php: Undefined class constant 'TYPE_STRING'
Backtrace:
#0 ../extensions/TitleIcon/TitleIcon.php(224): TitleIcon->getPropertyValues(Title, string)
#1 ../extensions/TitleIcon/TitleIcon.php(161): TitleIcon->getIcons()
#2 ../extensions/TitleIcon/TitleIcon.php(138): TitleIcon->getIconHTML()
#3 ../extensions/TitleIcon/TitleIcon.php(74): TitleIcon->handlePageTitle(OutputPage)
#4 ../includes/Hooks.php(177): TitleIcon::showIconInPageTitle(OutputPage, SkinChameleon)
#5 ../includes/Hooks.php(237): Hooks::callHook(string, array, array, NULL, string)
#6 ../includes/OutputPage.php(2385): Hooks::runWithoutAbort(string, array)
#7 ../includes/MediaWiki.php(868): OutputPage->output(boolean)
#8 ../includes/MediaWiki.php(880): MediaWiki->{closure}()
#9 ../includes/MediaWiki.php(524): MediaWiki->main()
#10 ../index.php(42): MediaWiki->run()
#11 {main}