Show warning in version check and error reporting are not available

When curl is missing and allow_url_fopen is disabled, we can not access
remote files.

Fixes #11874

Signed-off-by: Michal Čihař <michal@cihar.com>

ChangeLog

@@ -35,6 +35,7 @@ phpMyAdmin - ChangeLog
 + issue #11789 Show MySQL error messages in user language
 + issue        Add 'ssl_verify' configuration directive for self-signed certificates with mysqlnd and PHP >= 5.6
 + issue #11874 Show more used PHP extensions
+- issue #11874 Report when version check and error reporting are disabled
 
 4.5.5.0 (not yet released)
 - issue        Undefined index: is_ajax_request

index.php

@@ -475,6 +475,19 @@ if (! @extension_loaded('mbstring')) {
     );
 }
 
+/**
+ * Missing functionality
+ */
+if (! extension_loaded('curl') && ! ini_get('allow_url_fopen')) {
+    trigger_error(
+        __(
+            'The curl extension was not found and allow_url_fopen is '
+            . 'disabled. Due to this some features such as error reporting '
+            . 'or version check are disabled.'
+        )
+    );
+}
+
 if ($cfg['LoginCookieValidityDisableWarning'] == false) {
     /**
      * Check whether session.gc_maxlifetime limits session validity.