No podemos actualizar el Php

Hola, actualmente usamos PHP 5.6, Hemos actualizado la versión de wordpress que nos indica que hay que actualizar la versión de php. Cuando lo hacemos la página carga un error crítico.
Parece que es debido al revslider. Qué debemos hacer?

Hello, we currently use PHP 5.6, We have updated the version of wordpress that indicates that we must update the version of php. When we do, the page loads a critical error.
It seems to be due to the revslider. What should we do?

Error:
[Fri Jul 24 07:49:37.751394 2020] [proxy_fcgi:error] [pid 9842:tid 139654636443392] [client 47.63.8.136:0] AH01071: Got error ‘PHP message: PHP Fatal error: Uncaught Error: [] operator not supported for strings in /home/huertacamp/domains/huertacampojara.es/public_html/wp-content/plugins/revslider/includes/framework/base-admin.class.php:69\nStack trace:\n#0 /home/huertacamp/domains/huertacampojara.es/public_html/wp-content/plugins/revslider/admin/revslider-admin.class.php(393): RevSliderBaseAdmin::addMetaBox(‘Revolution Slid…’, ”, Array, NULL)\n#1 /home/huertacamp/domains/huertacampojara.es/public_html/wp-content/plugins/revslider/admin/revslider-admin.class.php(65): RevSliderAdmin->addSliderMetaBox()\n#2 /home/huertacamp/domains/huertacampojara.es/public_html/wp-content/plugins/revslider/admin/revslider-admin.class.php(43): RevSliderAdmin->init()\n#3 /home/huertacamp/domains/huertacampojara.es/public_html/wp-content/plugins/revslider/revslider.php(150): RevSliderAdmin->__construct(‘/home/huertacam…’)\n#4 /home/huertacamp/domains/huertacampojara.es/public_html/wp-settings.php(371): include_once(‘/home/huertacam…’)\n#5 /h…’, referer: https://www.huertacampojara.es/wp-admin/plugins.php
[Fri Jul 24 07:49:46.309926 2020] [proxy_fcgi:error] [pid 10341:tid 139654586087168] [client 47.63.8.136:0] AH01071: Got error ‘PHP message: PHP Fatal error: Uncaught Error: [] operator not supported for strings in /home/huertacamp/domains/huertacampojara.es/public_html/wp-content/plugins/revslider/includes/framework/base-admin.class.php:69\nStack trace:\n#0 /home/huertacamp/domains/huertacampojara.es/public_html/wp-content/plugins/revslider/admin/revslider-admin.class.php(393): RevSliderBaseAdmin::addMetaBox(‘Revolution Slid…’, ”, Array, NULL)\n#1 /home/huertacamp/domains/huertacampojara.es/public_html/wp-content/plugins/revslider/admin/revslider-admin.class.php(65): RevSliderAdmin->addSliderMetaBox()\n#2 /home/huertacamp/domains/huertacampojara.es/public_html/wp-content/plugins/revslider/admin/revslider-admin.class.php(43): RevSliderAdmin->init()\n#3 /home/huertacamp/domains/huertacampojara.es/public_html/wp-content/plugins/revslider/revslider.php(150): RevSliderAdmin->__construct(‘/home/huertacam…’)\n#4 /home/huertacamp/domains/huertacampojara.es/public_html/wp-settings.php(371): include_once(‘/home/huertacam…’)\n#5 /h…’, referer: https://www.huertacampojara.es/wp-admin/admin.php?page=wpcf7