Complete PHPStan Level 6 (#5305)

* Complete PHPStan Level 6
Fix https://github.com/FreshRSS/FreshRSS/issues/4112
And initiate PHPStan Level 7

* PHPStan Level 6 for tests
* Use phpstan/phpstan-phpunit
* Update to PHPStan version 1.10

* Fix mixed bug

* Fix mixed return bug

* Fix paginator bug

* Fix FreshRSS_UserConfiguration

* A couple more Minz_Configuration bug fixes

* A few trivial PHPStan Level 7 fixes

* A few more simple PHPStan Level 7

* More files passing PHPStan Level 7
Add interface to replace removed class from https://github.com/FreshRSS/FreshRSS/pull/5251

* A few more PHPStan Level 7 preparations

* A few last details

3 files changed, 12 insertions, 13 deletions

diff --git a/p/api/fever.php b/p/api/fever.php
index 1d3fa6f05..26efe841b 100644
--- a/p/api/fever.php
+++ b/p/api/fever.php
@@ -336,9 +336,8 @@ final class FeverAPI
 		$groups = array();
 
 		$categoryDAO = FreshRSS_Factory::createCategoryDao();
-		$categories = $categoryDAO->listCategories(false, false);
+		$categories = $categoryDAO->listCategories(false, false) ?: [];
 
-		/** @var FreshRSS_Category $category */
 		foreach ($categories as $category) {
 			$groups[] = array(
 				'id' => $category->id(),
@@ -430,28 +429,28 @@ final class FeverAPI
 	}
 
 	/**
-	 * @return integer|false
+	 * @return int|false
 	 */
 	private function setItemAsRead(string $id) {
 		return $this->entryDAO->markRead($id, true);
 	}
 
 	/**
-	 * @return integer|false
+	 * @return int|false
 	 */
 	private function setItemAsUnread(string $id) {
 		return $this->entryDAO->markRead($id, false);
 	}
 
 	/**
-	 * @return integer|false
+	 * @return int|false
 	 */
 	private function setItemAsSaved(string $id) {
 		return $this->entryDAO->markFavorite($id, true);
 	}
 
 	/**
-	 * @return integer|false
+	 * @return int|false
 	 */
 	private function setItemAsUnsaved(string $id) {
 		return $this->entryDAO->markFavorite($id, false);
@@ -540,7 +539,7 @@ final class FeverAPI
 	}
 
 	/**
-	 * @return integer|false
+	 * @return int|false
 	 */
 	private function setFeedAsRead(int $id, int $before) {
 		$before = $this->convertBeforeToId($before);
@@ -548,7 +547,7 @@ final class FeverAPI
 	}
 
 	/**
-	 * @return integer|false
+	 * @return int|false
 	 */
 	private function setGroupAsRead(int $id, int $before) {
 		$before = $this->convertBeforeToId($before);
diff --git a/p/f.php b/p/f.php
index 6e30b64b2..43905775a 100644
--- a/p/f.php
+++ b/p/f.php
@@ -5,7 +5,7 @@ require(LIB_PATH . '/favicons.php');
 require(LIB_PATH . '/http-conditional.php');
 
 function show_default_favicon(int $cacheSeconds = 3600): void {
-	$default_mtime = @filemtime(DEFAULT_FAVICON);
+	$default_mtime = @filemtime(DEFAULT_FAVICON) ?: 0;
 	if (!httpConditional($default_mtime, $cacheSeconds, 2)) {
 		header('Content-Type: image/x-icon');
 		header('Content-Disposition: inline; filename="default_favicon.ico"');
@@ -21,8 +21,8 @@ if (!ctype_xdigit($id)) {
 $txt = FAVICONS_DIR . $id . '.txt';
 $ico = FAVICONS_DIR . $id . '.ico';
 
-$ico_mtime = @filemtime($ico);
-$txt_mtime = @filemtime($txt);
+$ico_mtime = @filemtime($ico) ?: 0;
+$txt_mtime = @filemtime($txt) ?: 0;
 
 if ($ico_mtime == false || $ico_mtime < $txt_mtime || ($ico_mtime < time() - (mt_rand(15, 20) * 86400))) {
 	if ($txt_mtime == false) {
diff --git a/p/i/index.php b/p/i/index.php
index 690b1b1b1..6814a224f 100644
--- a/p/i/index.php
+++ b/p/i/index.php
@@ -35,8 +35,8 @@ if (!file_exists($applied_migrations_path)) {
 		require(LIB_PATH . '/http-conditional.php');
 		$currentUser = Minz_User::name();
 		$dateLastModification = $currentUser === null ? time() : max(
-			@filemtime(USERS_PATH . '/' . $currentUser . '/' . LOG_FILENAME),
-			@filemtime(DATA_PATH . '/config.php')
+			@filemtime(USERS_PATH . '/' . $currentUser . '/' . LOG_FILENAME) ?: 0,
+			@filemtime(DATA_PATH . '/config.php') ?: 0
 		);
 		if (httpConditional($dateLastModification, 0, 0, false, PHP_COMPRESSION, true)) {
 			Minz_Session::init('FreshRSS');