A few more PHP8.1 fixes (#17989)

* add return type declartions #17686

should not break anything and gets rid of a warning

* add return type to method signature #17686

* annotate return types to avoid warnings

* add more return types

* upgrade phpmailer/phpmailer to 6.5.1

* add return types, avoid deprecated null to string conversion

* fix some deprecation warnings for php 8.1 #17686

* fix in DbHelper::getInstallVersion() instead #17686

* ensure empty(DbHelper::getInstallVersion()) succeed #17686

* force return "0" string and adjust test

Co-authored-by: Justin Velluppillai <justin@innocraft.com>

14 files changed, 36 insertions, 27 deletions

diff --git a/composer.lock b/composer.lock
index 56df2766fe..0e57d9dbad 100644
--- a/composer.lock
+++ b/composer.lock
@@ -1436,16 +1436,16 @@
         },
         {
             "name": "phpmailer/phpmailer",
-            "version": "v6.5.0",
+            "version": "v6.5.1",
             "source": {
                 "type": "git",
                 "url": "https://github.com/PHPMailer/PHPMailer.git",
-                "reference": "a5b5c43e50b7fba655f793ad27303cd74c57363c"
+                "reference": "dd803df5ad7492e1b40637f7ebd258fee5ca7355"
             },
             "dist": {
                 "type": "zip",
-                "url": "https://api.github.com/repos/PHPMailer/PHPMailer/zipball/a5b5c43e50b7fba655f793ad27303cd74c57363c",
-                "reference": "a5b5c43e50b7fba655f793ad27303cd74c57363c",
+                "url": "https://api.github.com/repos/PHPMailer/PHPMailer/zipball/dd803df5ad7492e1b40637f7ebd258fee5ca7355",
+                "reference": "dd803df5ad7492e1b40637f7ebd258fee5ca7355",
                 "shasum": ""
             },
             "require": {
@@ -1457,10 +1457,12 @@
             "require-dev": {
                 "dealerdirect/phpcodesniffer-composer-installer": "^0.7.0",
                 "doctrine/annotations": "^1.2",
+                "php-parallel-lint/php-console-highlighter": "^0.5.0",
+                "php-parallel-lint/php-parallel-lint": "^1.3",
                 "phpcompatibility/php-compatibility": "^9.3.5",
                 "roave/security-advisories": "dev-latest",
-                "squizlabs/php_codesniffer": "^3.5.6",
-                "yoast/phpunit-polyfills": "^0.2.0"
+                "squizlabs/php_codesniffer": "^3.6.0",
+                "yoast/phpunit-polyfills": "^1.0.0"
             },
             "suggest": {
                 "ext-mbstring": "Needed to send email in multibyte encoding charset or decode encoded addresses",
@@ -1500,7 +1502,7 @@
             "description": "PHPMailer is a full-featured email creation and transfer class for PHP",
             "support": {
                 "issues": "https://github.com/PHPMailer/PHPMailer/issues",
-                "source": "https://github.com/PHPMailer/PHPMailer/tree/v6.5.0"
+                "source": "https://github.com/PHPMailer/PHPMailer/tree/v6.5.1"
             },
             "funding": [
                 {
@@ -1508,7 +1510,7 @@
                     "type": "github"
                 }
             ],
-            "time": "2021-06-16T14:33:43+00:00"
+            "time": "2021-08-18T09:14:16+00:00"
         },
         {
             "name": "psr/container",
diff --git a/core/DataTable.php b/core/DataTable.php
index 3442e4ff08..6da6fadaa8 100644
--- a/core/DataTable.php
+++ b/core/DataTable.php
@@ -1983,29 +1983,29 @@ class DataTable implements DataTableInterface, \IteratorAggregate, \ArrayAccess
     /**
      * @return \ArrayIterator|Row[]
      */
-    public function getIterator()
+    public function getIterator(): \ArrayIterator
     {
         return new \ArrayIterator($this->getRows());
     }
 
-    public function offsetExists($offset)
+    public function offsetExists($offset): bool
     {
         $row = $this->getRowFromId($offset);
 
         return false !== $row;
     }
 
-    public function offsetGet($offset)
+    public function offsetGet($offset): Row
     {
         return $this->getRowFromId($offset);
     }
 
-    public function offsetSet($offset, $value)
+    public function offsetSet($offset, $value): void
     {
         $this->rows[$offset] = $value;
     }
 
-    public function offsetUnset($offset)
+    public function offsetUnset($offset): void
     {
         $this->deleteRow($offset);
     }
diff --git a/core/DbHelper.php b/core/DbHelper.php
index ea0b4e5e4e..17756acdfc 100644
--- a/core/DbHelper.php
+++ b/core/DbHelper.php
@@ -118,9 +118,13 @@ class DbHelper
     /**
      * Returns which Matomo version was used to install this Matomo for the first time.
      */
-    public static function getInstallVersion()
+    public static function getInstallVersion(): string
     {
-        return Schema::getInstance()->getInstallVersion();
+        return Schema::getInstance()->getInstallVersion() ?? '0';
+        // need string as usage is usually
+        // version_compare(DbHelper::getInstallVersion(),'4.0.0-b1', '<') or similar
+        // and PHP 8.1 throws a deprecation warning otherwise
+        // @see https://github.com/matomo-org/matomo/pull/17989#issuecomment-921298360
     }
 
     public static function wasMatomoInstalledBeforeVersion($version)
@@ -322,4 +326,4 @@ class DbHelper
         return (0 !== preg_match('/(^[a-zA-Z0-9]+([a-zA-Z0-9\_\.\-\+]*))$/D', $dbname));
     }
 
-}
+}
\ No newline at end of file
diff --git a/libs/Zend/Db/Statement/Pdo.php b/libs/Zend/Db/Statement/Pdo.php
index fb501eaf30..6869582023 100644
--- a/libs/Zend/Db/Statement/Pdo.php
+++ b/libs/Zend/Db/Statement/Pdo.php
@@ -264,7 +264,7 @@ class Zend_Db_Statement_Pdo extends Zend_Db_Statement implements IteratorAggrega
      *
      * @return IteratorIterator
      */
-    public function getIterator()
+    public function getIterator(): IteratorIterator
     {
         return new IteratorIterator($this->_stmt);
     }
diff --git a/libs/Zend/Session/Namespace.php b/libs/Zend/Session/Namespace.php
index dfa680233f..d16ed65e45 100644
--- a/libs/Zend/Session/Namespace.php
+++ b/libs/Zend/Session/Namespace.php
@@ -207,7 +207,7 @@ class Zend_Session_Namespace extends Zend_Session_Abstract implements IteratorAg
      *
      * @return ArrayObject - iteratable container of the namespace contents
      */
-    public function getIterator()
+    public function getIterator(): ArrayObject
     {
         return new ArrayObject(parent::_namespaceGetAll($this->_namespace));
     }
diff --git a/plugins/DevicePlugins/API.php b/plugins/DevicePlugins/API.php
index b767d5ade5..99109f72aa 100644
--- a/plugins/DevicePlugins/API.php
+++ b/plugins/DevicePlugins/API.php
@@ -86,6 +86,7 @@ class API extends \Piwik\Plugin\API
             $visitsSum = $visitsSumTotal - $ieVisits;
 
             $extraProcessedMetrics = $table->getMetadata(DataTable::EXTRA_PROCESSED_METRICS_METADATA_NAME);
+            $extraProcessedMetrics = is_array($extraProcessedMetrics) ? $extraProcessedMetrics : [];
             $extraProcessedMetrics[] = new VisitsPercent($visitsSum);
             $table->setMetadata(DataTable::EXTRA_PROCESSED_METRICS_METADATA_NAME, $extraProcessedMetrics);
         }
diff --git a/plugins/MultiSites/API.php b/plugins/MultiSites/API.php
index 5a12e71a0d..a0e20a470c 100644
--- a/plugins/MultiSites/API.php
+++ b/plugins/MultiSites/API.php
@@ -353,6 +353,7 @@ class API extends \Piwik\Plugin\API
                                       ? "Piwik\\Plugins\\MultiSites\\Columns\\Metrics\\EcommerceOnlyEvolutionMetric"
                                       : "Piwik\\Plugins\\CoreHome\\Columns\\Metrics\\EvolutionMetric";
 
+                $extraProcessedMetrics = is_array($extraProcessedMetrics) ? $extraProcessedMetrics : [];
                 $extraProcessedMetrics[] = new $evolutionMetricClass(
                     $metricSettings[self::METRIC_RECORD_NAME_KEY],
                     $pastData,
diff --git a/plugins/Referrers/VisitorDetails.php b/plugins/Referrers/VisitorDetails.php
index df571bf5f3..ece8dc40fe 100644
--- a/plugins/Referrers/VisitorDetails.php
+++ b/plugins/Referrers/VisitorDetails.php
@@ -94,9 +94,9 @@ class VisitorDetails extends VisitorDetailsAbstract
         return null;
     }
 
-    protected function getReferrerName()
+    protected function getReferrerName(): string
     {
-        return urldecode($this->details['referer_name']);
+        return urldecode($this->details['referer_name'] ?? '');
     }
 
     protected function getSearchEngineUrl()
diff --git a/plugins/SEO/Metric/Alexa.php b/plugins/SEO/Metric/Alexa.php
index b0d3a42c6b..a9a58160e0 100644
--- a/plugins/SEO/Metric/Alexa.php
+++ b/plugins/SEO/Metric/Alexa.php
@@ -35,7 +35,7 @@ class Alexa implements MetricsProvider
     {
         $value = null;
         try {
-            $response = Http::sendHttpRequest(self::URL . urlencode($domain), $timeout = 10, @$_SERVER['HTTP_USER_AGENT']);
+            $response = Http::sendHttpRequest(self::URL . urlencode($domain ?? ''), $timeout = 10, @$_SERVER['HTTP_USER_AGENT']);
             libxml_use_internal_errors(true); // suppress errors
             $dom = new \DomDocument();
             $dom->loadHTML($response);
@@ -54,7 +54,7 @@ class Alexa implements MetricsProvider
         }
 
         $logo = "plugins/Morpheus/icons/dist/SEO/alexa.com.png";
-        $link = self::LINK . urlencode($domain);
+        $link = self::LINK . urlencode($domain ?? '');
 
         return array(
             new Metric('alexa', 'SEO_AlexaRank', $value, $logo, $link)
diff --git a/plugins/SEO/Metric/Bing.php b/plugins/SEO/Metric/Bing.php
index ab7b1bce88..1279b77894 100644
--- a/plugins/SEO/Metric/Bing.php
+++ b/plugins/SEO/Metric/Bing.php
@@ -32,7 +32,7 @@ class Bing implements MetricsProvider
 
     public function getMetrics($domain)
     {
-        $url = self::URL . urlencode($domain);
+        $url = self::URL . urlencode($domain ?? '');
 
         try {
             $response = str_replace('&nbsp;', ' ', Http::sendHttpRequest($url, $timeout = 10, @$_SERVER['HTTP_USER_AGENT']));
diff --git a/plugins/SEO/Metric/DomainAge.php b/plugins/SEO/Metric/DomainAge.php
index 8d5d4bc4b8..0753e8eb89 100644
--- a/plugins/SEO/Metric/DomainAge.php
+++ b/plugins/SEO/Metric/DomainAge.php
@@ -35,7 +35,7 @@ class DomainAge implements MetricsProvider
 
     public function getMetrics($domain)
     {
-        $domain  = str_replace('www.', '', $domain);
+        $domain  = str_replace('www.', '', $domain ?? '');
 
         $ages = array();
 
diff --git a/plugins/SEO/Metric/Google.php b/plugins/SEO/Metric/Google.php
index 2edf5afc23..14f6e3d9f2 100644
--- a/plugins/SEO/Metric/Google.php
+++ b/plugins/SEO/Metric/Google.php
@@ -46,7 +46,7 @@ class Google implements MetricsProvider
 
     public function fetchIndexedPagesCount($domain)
     {
-        $url = self::SEARCH_URL . urlencode($domain);
+        $url = self::SEARCH_URL . urlencode($domain ?? '');
 
         try {
             $response = str_replace('&nbsp;', ' ', Http::sendHttpRequest($url, $timeout = 10, @$_SERVER['HTTP_USER_AGENT']));
diff --git a/plugins/SEO/Metric/ProviderCache.php b/plugins/SEO/Metric/ProviderCache.php
index 98b4c08fa0..898a19a6fd 100644
--- a/plugins/SEO/Metric/ProviderCache.php
+++ b/plugins/SEO/Metric/ProviderCache.php
@@ -34,7 +34,7 @@ class ProviderCache implements MetricsProvider
 
     public function getMetrics($domain)
     {
-        $cacheId = 'SEO_getRank_' . md5($domain);
+        $cacheId = 'SEO_getRank_' . md5($domain ?? '');
 
         $metrics = $this->cache->fetch($cacheId);
 
diff --git a/tests/PHPUnit/Integration/DbHelperTest.php b/tests/PHPUnit/Integration/DbHelperTest.php
index c08553ea87..57c8d0e7fe 100644
--- a/tests/PHPUnit/Integration/DbHelperTest.php
+++ b/tests/PHPUnit/Integration/DbHelperTest.php
@@ -40,7 +40,8 @@ class DbHelperTest extends IntegrationTestCase
     public function test_recordInstallVersion_setsCurrentVersion()
     {
         Option::delete(Db\Schema\Mysql::OPTION_NAME_MATOMO_INSTALL_VERSION);
-        $this->assertNull(DbHelper::getInstallVersion());
+        $this->assertEmpty(DbHelper::getInstallVersion());
+        $this->assertEquals('0', DbHelper::getInstallVersion()); // since php 8.1 this is required
 
         DbHelper::recordInstallVersion();
         $this->assertSame(Version::VERSION, DbHelper::getInstallVersion());