Convert eight variable assignments to the usage of combined operators

[elfring]

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

diff --git a/includes/ConfigHelper.php b/includes/ConfigHelper.php
index e0145dc..57965ad 100644
--- a/includes/ConfigHelper.php
+++ b/includes/ConfigHelper.php
@@ -532,13 +532,13 @@ final class ConfigHelper {
         ini_set('memory_limit', $memory_limit);
         if (preg_match('/G$/i',$memory_limit)) {
             $memory_limit = preg_replace('/G$/i','',$memory_limit);
-            $memory_limit = $memory_limit * 1024 * 1024 * 1024;
+            $memory_limit *= 1024 * 1024 * 1024;
         } else if (preg_match('/M$/i',$memory_limit)) {
             $memory_limit = preg_replace('/M$/i','',$memory_limit);
-            $memory_limit = $memory_limit * 1024 * 1024;
+            $memory_limit *= 1024 * 1024;
         } else if (preg_match('/K$/i',$memory_limit)) {
             $memory_limit = preg_replace('/K$/i','',$memory_limit);
-            $memory_limit = $memory_limit * 1024;
+            $memory_limit *= 1024;
         }
         Config::set(CONFIG_MEMORY_LIMIT, $memory_limit);
 
diff --git a/includes/StoragePool.php b/includes/StoragePool.php
index 9c538b2..2b85017 100644
--- a/includes/StoragePool.php
+++ b/includes/StoragePool.php
@@ -128,7 +128,7 @@ final class StoragePool {
             $body .= "\nA fsck will now start, to fix the symlinks found in your shares, when possible.\nYou'll receive a report email once that fsck run completes.\n";
             $drive_string = join(", ", $returned_drives);
             $subject = "Storage pool drive now online on " . exec ('hostname') . ": ";
-            $subject = $subject . $drive_string;
+            $subject .= $drive_string;
             if (strlen($subject) > 255) {
                 $subject = substr($subject, 0, 255);
             }
@@ -157,7 +157,7 @@ final class StoragePool {
             $body .= "A fsck will now start, to fix the symlinks found in your shares, when possible.\nYou'll receive a report email once that fsck run completes.\n";
             $subject = "Missing storage pool drives on " . exec('hostname') . ": ";
             $drive_string = join(",",$missing_drives);
-            $subject = $subject . $drive_string;
+            $subject .= $drive_string;
             if (strlen($subject) > 255) {
                 $subject = substr($subject, 0, 255);
             }
diff --git a/includes/common.php b/includes/common.php
index 519d295..b821cb9 100644
--- a/includes/common.php
+++ b/includes/common.php
@@ -209,7 +209,7 @@ function get_share_landing_zone($share) {
 function memory_check() {
     $usage = memory_get_usage();
     $used = $usage / Config::get(CONFIG_MEMORY_LIMIT);
-    $used = $used * 100;
+    $used *= 100;
     if ($used > 95) {
         Log::critical("$used% memory usage, exiting. Please increase '" . CONFIG_MEMORY_LIMIT . "' in " . ConfigHelper::$config_file, Log::EVENT_CODE_MEMORY_LIMIT_REACHED);
     }
@@ -934,9 +934,9 @@ function how_long_ago($past_time) {
             $ago = $h . "h ";
             $m -= $h * 60;
         }
-        $ago = $ago . $m . "m ";
+        $ago .= $m . "m ";
     }
-    $ago = $ago . $s . "s";
+    $ago .= $s . "s";
     if ($ago == '0s') {
         return 'just now';
     }