Convert five variable assignments to the usage of combined operators

[elfring]

👀 Some source code analysis tools can help to find opportunities for improving software components.
💭 I propose to increase the usage of combined operators accordingly.

diff --git a/lib/eventum/class.language.php b/lib/eventum/class.language.php
index 4b532d6bb..8d4b3b9aa 100644
--- a/lib/eventum/class.language.php
+++ b/lib/eventum/class.language.php
@@ -149,7 +149,7 @@ class Language
     {
         // XXX do not append charset to en_US locale
         if ($locale !== 'en_US') {
-            $locale = $locale . '.' . self::CHARSET;
+            $locale .= '.' . self::CHARSET;
         }
         $res = setlocale(LC_TIME, $locale);
         if ($res === false) {
diff --git a/lib/eventum/class.reminder.php b/lib/eventum/class.reminder.php
index b3bf7a185..707edd9e7 100644
--- a/lib/eventum/class.reminder.php
+++ b/lib/eventum/class.reminder.php
@@ -918,7 +918,7 @@ class Reminder
                             $cond['rmf_sql_field'] . ')';
                         $cond['rlc_value'] = 'UNIX_TIMESTAMP()';
                     } else {
-                        $cond['rlc_value'] = $cond['rlc_value'] * 60 * 60;
+                        $cond['rlc_value'] *= 60 * 60;
                         if (@$reminder['rem_skip_weekend'] == 1) {
                             $sql_field = Reminder_Condition::getSQLField($cond['rlc_rmf_id']);
                             $cond['rmf_sql_representation'] = DB_Helper::getNoWeekendDateDiffSQL($sql_field);
diff --git a/src/Db/AbstractMigration.php b/src/Db/AbstractMigration.php
index 759cdcece..5d8292caa 100644
--- a/src/Db/AbstractMigration.php
+++ b/src/Db/AbstractMigration.php
@@ -90,9 +90,9 @@ abstract class AbstractMigration extends PhinxAbstractMigration
      */
     public function table($tableName, $options = []): Table
     {
-        $options['engine'] = $options['engine'] ?? $this->engine;
-        $options['charset'] = $options['charset'] ?? $this->charset;
-        $options['collation'] = $options['collation'] ?? $this->collation;
+        $options['engine'] ??= $this->engine;
+        $options['charset'] ??= $this->charset;
+        $options['collation'] ??= $this->collation;
 
         return parent::table($tableName, $options);
     }