Here is the error log. Please see the Fatal Error with Smarty and kindly advise.
[03-Apr-2019 08:18:56 America/Los_Angeles] PHP Warning: Declaration of InstallHandler::validate($request) should be compatible with PKPHandler::validate($requiredContexts = NULL, $request = NULL) in /home/aaaior5/public_html/ojslatest/lib/pkp/pages/install/InstallHandler.inc.php on line 118
[03-Apr-2019 08:18:56 America/Los_Angeles] PHP Warning: Cannot modify header information - headers already sent by (output started at /home/aaaior5/public_html/ojslatest/lib/pkp/pages/install/InstallHandler.inc.php:118) in /home/aaaior5/public_html/ojslatest/lib/pkp/classes/template/PKPTemplateManager.inc.php on line 836
[03-Apr-2019 08:18:56 America/Los_Angeles] PHP Warning: Cannot modify header information - headers already sent by (output started at /home/aaaior5/public_html/ojslatest/lib/pkp/pages/install/InstallHandler.inc.php:118) in /home/aaaior5/public_html/ojslatest/lib/pkp/classes/template/PKPTemplateManager.inc.php on line 837
[03-Apr-2019 08:18:56 America/Los_Angeles] PHP Fatal error: Uncaught Error: Call to undefined function mb_split() in /home/aaaior5/public_html/ojslatest/lib/pkp/lib/vendor/smarty/smarty/libs/plugins/shared.mb_str_replace.php:47
Stack trace:
#0 /home/aaaior5/public_html/ojslatest/lib/pkp/lib/vendor/smarty/smarty/libs/plugins/modifier.replace.php(34): smarty_mb_str_replace('_', '-', 'en_US')
#1 /home/aaaior5/public_html/ojslatest/cache/t_compile/13376d7934b5f251160733e5e3c8b2ff6a1e1f24^652202841b9a358b5663534995b87eb1fcc7545d_0.core.commonheader.tpl.php(29): smarty_modifier_replace('en_US', '_', '-')
#2 /home/aaaior5/public_html/ojslatest/lib/pkp/lib/vendor/smarty/smarty/libs/sysplugins/smarty_template_resource_base.php(123): content_5ca02179d23940_10097313(Object(Smarty_Internal_Template))
#3 /home/aaaior5/public_html/ojslatest/lib/pkp/lib/vendor/smarty/smarty/libs/sysplugins/smarty_template_compiled.php(114): Smarty_Template_Resource_Base->getRenderedTemplateCode(Object(Smarty_Internal_Template))
#4 /home/aaaior5/public_html/ojslatest/lib/pkp/lib/vendor/smarty/smarty/ in /home/aaaior5/public_html/ojslatest/lib/pkp/lib/vendor/smarty/smarty/libs/plugins/shared.mb_str_replace.php on line 47