Error Received When Opening Any Attachment

When I try to open any attachment, I get the below error. I deactivated all plugins but still get the error.

“The site is experiencing technical difficulties. Please check your site admin email inbox for instructions.”

Here are the error details:

Error Details
=============

An error of type E_ERROR was caused in line 542 of the file /home/antolrxc/public_html/wp-content/plugins/apply-online/admin/class-applyonline-admin.php. Error message: Uncaught Error: Call to undefined function mime_content_type() in /home/antolrxc/public_html/wp-content/plugins/apply-online/admin/class-applyonline-admin.php:542
Stack trace:
#0 /home/antolrxc/public_html/wp-includes/class-wp-hook.php(286): Applyonline_Admin->output_attachment(”)
#1 /home/antolrxc/public_html/wp-includes/class-wp-hook.php(310): WP_Hook->apply_filters(NULL, Array)
#2 /home/antolrxc/public_html/wp-includes/plugin.php(465): WP_Hook->do_action(Array)
#3 /home/antolrxc/public_html/wp-includes/pluggable.php(47): do_action(‘set_current_use…’)
#4 /home/antolrxc/public_html/wp-includes/user.php(2704): wp_set_current_user(2)
#5 /home/antolrxc/public_html/wp-includes/pluggable.php(69): _wp_get_current_user()
#6 /home/antolrxc/public_html/wp-includes/l10n.php(92): wp_get_current_user()
#7 /home/antolrxc/public_html/wp-includes/l10n.php(134): get_user_locale()
#8 /home/antolrxc/public_html/wp-includes/l10n.php(786): determine_locale()
#9 /home/antolrxc/public_html/wp-content/plugins/apply-online/inclu