Upgrade to PHP 7

Hi,

I have just upgraded my server to use EasyApache 4, which means I can venture into the wonderful world of PHP7. However when I switch to 7 I am getting the following error:

[24-Jan-2017 16:17:23 UTC] PHP Fatal error:  Uncaught Error: Call to undefined function Symfony\Polyfill\Mbstring\iconv_strlen() in /home/newgatewatches/public_html/admin/addons/apps/perch_shop/lib/vendor/symfony/polyfill-mbstring/Mbstring.php:338
Stack trace:
#0 /home/newgatewatches/public_html/admin/addons/apps/perch_shop/lib/vendor/symfony/polyfill-mbstring/bootstrap.php(31): Symfony\Polyfill\Mbstring\Mbstring::mb_strlen('</perch:repeate...', 'UTF-8')
#1 /home/newgatewatches/public_html/admin/core/lib/PerchTemplate.class.php(1662): mb_strlen('</perch:repeate...')
#2 /home/newgatewatches/public_html/admin/core/lib/PerchTemplate.class.php(1216): PerchTemplate->parse_paired_tags('repeater', false, '<meta name="des...', Array, false, 'render_repeater')
#3 /home/newgatewatches/public_html/admin/core/lib/PerchTemplate.class.php(166): PerchTemplate->parse_repeaters('<meta name="des...', Array)
#4 /home/newgatewatches/public_html/admin/core/apps/content/PerchContent_Page.class.php(238): PerchTemplate->render(Array)
#5 /home/newgatewatches/public_html/admin/c in /home/newgatewatches/public_html/admin/addons/apps/perch_shop/lib/vendor/symfony/polyfill-mbstring/Mbstring.php on line 338

I am guessing this is a server config thing so have taken it up with my hosts too, but thought I would ask here just in case anyone knew what the fix would be.

Thanks!

Mike