Whoops\Exception\ErrorException Array and string offset access syntax with curly braces is deprecated

i got this error message when i try to create to Extension DAHDI

(admin/config.php?display=extensions&tech_hardware=dahdi_generic )

Whoops\Exception\ErrorException thrown with message "Array and string offset access syntax with curly braces is deprecated"

Stacktrace:
#5 Whoops\Exception\ErrorException in /var/www/html/admin/modules/endpointman/includes/json.inc:232
#4 Whoops\Run:handleError in /var/www/html/admin/modules/endpointman/includes/functions.inc:36
#3 require_once in /var/www/html/admin/modules/endpointman/includes/functions.inc:36
#2 endpointmanager:__construct in /var/www/html/admin/modules/endpointman/functions.inc.php:89
#1 endpointman_configpageinit in /var/www/html/admin/libraries/BMO/GuiHooks.class.php:267
#0 FreePBX\GuiHooks:doConfigPageInits in /var/www/html/admin/config.php:445