thanks for you help i found out the json php was installed but not listed in etc/php/7.0/mods-available so i used sudo apt-get purge php-json then sudo apt-get install php-json is fixed my fault but now when i open up owncloud i get Internal Server Error my log looks like this
{"reqId":"jGyAYvqFvO+jX+OoRcal","remoteAddr":"192.168.1.3","app":"index","message":"Exception: {\"Exception\":\"Error\",\"Message\":\"Class 'PDO' not found\",\"Code\":0,\"Trace\":\"#0 \\/var\\/www\\/owncloud\\/lib\\/private\\/Setup.php(170): OC\\Setup->getAvailableDbDriversForPdo()\n#1 \\/var\\/www\\/owncloud\\/lib\\/private\\/legacy\\/util.php(642): OC\\Setup->getSupportedDatabases()\n#2 \\/var\\/www\\/owncloud\\/lib\\/base.php(587): OC_Util::checkServer(Object(OC\\AllConfig))\n#3 \\/var\\/www\\/owncloud\\/lib\\/base.php(973): OC::init()\n#4 \\/var\\/www\\/owncloud\\/index.php(37): require_once('\\/var\\/www\\/ownclo...')\n#5 {main}\",\"File\":\"\\/var\\/www\\/owncloud\\/lib\\/private\\/Setup.php\",\"Line\":114}","level":3,"time":"2016-11-06T11:03:56+00:00","method":"GET","url":"\/owncloud\/","user":"--"}
{"reqId":"jGyAYvqFvO+jX+OoRcal","remoteAddr":"192.168.1.3","app":"PHP","message":"PHP Startup: Unable to load dynamic library '\/usr\/lib\/php\/20151012\/pdo_sqlite.so' - \/usr\/lib\/php\/20151012\/pdo_sqlite.so: undefined symbol: php_pdo_unregister_driver at Unknown#0","level":3,"time":"2016-11-06T11:03:56+00:00","method":"GET","url":"\/owncloud\/","user":"--"}
i wouldn't be surprised if its another php problem as tried installing and uninstalling a good few times now so might have broken other php files