Application error

Error: Cannot send headers; headers already sent in /usr/www/users/fetnet/production/application/controllers/IndexController.php, line 1957;

Cannot send headers; headers already sent in /usr/www/users/fetnet/production/application/controllers/IndexController.php, line 1957
/library/Zend/Controller/Response/Abstract.php	throw new Zend_Controller_Response_Exception	Abstract.php : 323
/library/Zend/Controller/Response/Abstract.php	Zend_Controller_Response_Abstract->canSendHeaders ( '1')	Abstract.php : 341
/library/Zend/Controller/Response/Abstract.php	Zend_Controller_Response_Abstract->sendHeaders ( )	Abstract.php : 768
/library/Zend/Controller/Front.php	Zend_Controller_Response_Abstract->sendResponse ( )	Front.php : 992
/library/Zend/Application/Bootstrap/Bootstrap.php	Zend_Controller_Front->dispatch ( )	Bootstrap.php : 97
/library/Zend/Application.php	Zend_Application_Bootstrap_Bootstrap->run ( )	Application.php : 366
/public/modules/Core/index.php	Zend_Application->run ( )	index.php : 141
/public/index.php	require_once ( '/usr/www/users/fetnet/production/public/modules/Core/index.php')	index.php : 24

Request Parameters:

array(5) {
  ["controller"]=>
  string(5) "index"
  ["action"]=>
  string(13) "download-file"
  ["module"]=>
  string(3) "App"
  ["fullPath"]=>
  string(45) "/_uploads/5/f/0/5f0eb961e79e6/467831_abb3.jpg"
  ["fileName"]=>
  string(12) "467831-5.jpg"
}

Zend Version: 1.12.0
OS: Linux dedi5079.your-server.de 4.19.0-14-amd64 #1 SMP Debian 4.19.171-2 (2021-01-30) x86_64
PHP Version: 5.6.40
Magic Quotes: 0

$_SERVER Dump:

array(85) {
  ["MAGICK_TEMPORARY_PATH"]=>
  string(21) "/usr/home/fetnet/.tmp"
  ["TMPDIR"]=>
  string(21) "/usr/home/fetnet/.tmp"
  ["PHP_FCGI_MAX_REQUESTS"]=>
  string(6) "100000"
  ["PATH"]=>
  string(60) "/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin"
  ["PHPRC"]=>
  string(28) "/home/httpd/php56-ini/fetnet"
  ["PWD"]=>
  string(19) "/home/httpd/cgi-bin"
  ["MAGICK_TMPDIR"]=>
  string(21) "/usr/home/fetnet/.tmp"
  ["CONTENT_LENGTH"]=>
  string(1) "0"
  ["HTTP_CONNECTION"]=>
  string(5) "close"
  ["SCRIPT_NAME"]=>
  string(17) "/public/index.php"
  ["REQUEST_URI"]=>
  string(109) "/index/download-file?fullPath=%2F_uploads%2F5%2Ff%2F0%2F5f0eb961e79e6%2F467831_abb3.jpg&fileName=467831-5.jpg"
  ["QUERY_STRING"]=>
  string(88) "fullPath=%2F_uploads%2F5%2Ff%2F0%2F5f0eb961e79e6%2F467831_abb3.jpg&fileName=467831-5.jpg"
  ["REQUEST_METHOD"]=>
  string(3) "GET"
  ["SERVER_PROTOCOL"]=>
  string(8) "HTTP/2.0"
  ["GATEWAY_INTERFACE"]=>
  string(7) "CGI/1.1"
  ["REDIRECT_QUERY_STRING"]=>
  string(88) "fullPath=%2F_uploads%2F5%2Ff%2F0%2F5f0eb961e79e6%2F467831_abb3.jpg&fileName=467831-5.jpg"
  ["REDIRECT_URL"]=>
  string(10) "/index.php"
  ["REMOTE_PORT"]=>
  string(5) "10400"
  ["SCRIPT_FILENAME"]=>
  string(49) "/usr/www/users/fetnet/production/public/index.php"
  ["SERVER_ADMIN"]=>
  string(25) "webmaster@shop.4smarts.eu"
  ["CONTEXT_DOCUMENT_ROOT"]=>
  string(32) "/usr/www/users/fetnet/production"
  ["CONTEXT_PREFIX"]=>
  string(0) ""
  ["REQUEST_SCHEME"]=>
  string(5) "https"
  ["DOCUMENT_ROOT"]=>
  string(32) "/usr/www/users/fetnet/production"
  ["REMOTE_ADDR"]=>
  string(13) "217.119.210.5"
  ["SERVER_PORT"]=>
  string(3) "443"
  ["SERVER_ADDR"]=>
  string(15) "136.243.123.163"
  ["SERVER_NAME"]=>
  string(15) "shop.4smarts.eu"
  ["SERVER_SOFTWARE"]=>
  string(6) "Apache"
  ["SERVER_SIGNATURE"]=>
  string(61) "Apache Server at shop.4smarts.eu Port 443
"
  ["HTTP_HOST"]=>
  string(15) "shop.4smarts.eu"
  ["HTTP_COOKIE"]=>
  string(251) "__utmz=167945699.1601391858.1.1.utmcsr=(direct)|utmccn=(direct)|utmcmd=(none); vid=5c73def43c147; __utmc=167945699; SID=1f1aef37df73e86ffb7dfa9792d376bb; __utma=167945699.257590839.1601391858.1612532066.1612538921.57; __utmb=167945699.12.10.1612538921"
  ["HTTP_ACCEPT_LANGUAGE"]=>
  string(35) "de-DE,de;q=0.9,en-US;q=0.8,en;q=0.7"
  ["HTTP_ACCEPT_ENCODING"]=>
  string(17) "gzip, deflate, br"
  ["HTTP_USER_AGENT"]=>
  string(115) "Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/88.0.4324.104 Safari/537.36"
  ["HTTP_REFERER"]=>
  string(129) "https://shop.4smarts.eu/index/shop/de/search.html?search=1&searchCategory=all&label=467831&sorting=relevance&articlesViewCount=50"
  ["HTTP_SEC_FETCH_DEST"]=>
  string(5) "empty"
  ["HTTP_SEC_FETCH_MODE"]=>
  string(8) "navigate"
  ["HTTP_SEC_FETCH_SITE"]=>
  string(11) "same-origin"
  ["SSL_TLS_SNI"]=>
  string(15) "shop.4smarts.eu"
  ["HTTPS"]=>
  string(2) "on"
  ["H2_STREAM_TAG"]=>
  string(5) "69-23"
  ["H2_STREAM_ID"]=>
  string(2) "23"
  ["H2_PUSHED_ON"]=>
  string(0) ""
  ["H2_PUSHED"]=>
  string(0) ""
  ["H2_PUSH"]=>
  string(2) "on"
  ["H2PUSH"]=>
  string(2) "on"
  ["HTTP2"]=>
  string(2) "on"
  ["REDIRECT_STATUS"]=>
  string(3) "200"
  ["REDIRECT_SSL_TLS_SNI"]=>
  string(15) "shop.4smarts.eu"
  ["REDIRECT_HTTPS"]=>
  string(2) "on"
  ["REDIRECT_H2_STREAM_TAG"]=>
  string(5) "69-23"
  ["REDIRECT_H2_STREAM_ID"]=>
  string(2) "23"
  ["REDIRECT_H2_PUSHED_ON"]=>
  string(0) ""
  ["REDIRECT_H2_PUSHED"]=>
  string(0) ""
  ["REDIRECT_H2_PUSH"]=>
  string(2) "on"
  ["REDIRECT_H2PUSH"]=>
  string(2) "on"
  ["REDIRECT_HTTP2"]=>
  string(2) "on"
  ["REDIRECT_REDIRECT_STATUS"]=>
  string(3) "200"
  ["REDIRECT_REDIRECT_SSL_TLS_SNI"]=>
  string(15) "shop.4smarts.eu"
  ["REDIRECT_REDIRECT_HTTPS"]=>
  string(2) "on"
  ["REDIRECT_REDIRECT_H2_STREAM_TAG"]=>
  string(5) "69-23"
  ["REDIRECT_REDIRECT_H2_STREAM_ID"]=>
  string(2) "23"
  ["REDIRECT_REDIRECT_H2_PUSHED_ON"]=>
  string(0) ""
  ["REDIRECT_REDIRECT_H2_PUSHED"]=>
  string(0) ""
  ["REDIRECT_REDIRECT_H2_PUSH"]=>
  string(2) "on"
  ["REDIRECT_REDIRECT_H2PUSH"]=>
  string(2) "on"
  ["REDIRECT_REDIRECT_HTTP2"]=>
  string(2) "on"
  ["REDIRECT_REDIRECT_REDIRECT_STATUS"]=>
  string(3) "200"
  ["REDIRECT_REDIRECT_REDIRECT_SSL_TLS_SNI"]=>
  string(15) "shop.4smarts.eu"
  ["REDIRECT_REDIRECT_REDIRECT_HTTPS"]=>
  string(2) "on"
  ["REDIRECT_REDIRECT_REDIRECT_H2_STREAM_TAG"]=>
  string(5) "69-23"
  ["REDIRECT_REDIRECT_REDIRECT_H2_STREAM_ID"]=>
  string(2) "23"
  ["REDIRECT_REDIRECT_REDIRECT_H2_PUSHED_ON"]=>
  string(0) ""
  ["REDIRECT_REDIRECT_REDIRECT_H2_PUSHED"]=>
  string(0) ""
  ["REDIRECT_REDIRECT_REDIRECT_H2_PUSH"]=>
  string(2) "on"
  ["REDIRECT_REDIRECT_REDIRECT_H2PUSH"]=>
  string(2) "on"
  ["REDIRECT_REDIRECT_REDIRECT_HTTP2"]=>
  string(2) "on"
  ["FCGI_ROLE"]=>
  string(9) "RESPONDER"
  ["PHP_SELF"]=>
  string(17) "/public/index.php"
  ["REQUEST_TIME_FLOAT"]=>
  float(1612539678.3974)
  ["REQUEST_TIME"]=>
  int(1612539678)
  ["argv"]=>
  array(1) {
    [0]=>
    string(88) "fullPath=%2F_uploads%2F5%2Ff%2F0%2F5f0eb961e79e6%2F467831_abb3.jpg&fileName=467831-5.jpg"
  }
  ["argc"]=>
  int(1)
  ["SCRIPT_URI"]=>
  string(42) "http://shop.4smarts.eu/index/download-file"
}