Fix PHP <5.6 syntax, fixes #8759, closes #8760

src/Composer/Command/SelfUpdateCommand.php

@@ -85,7 +85,7 @@ EOT
 
         // switch channel if requested
         $requestedChannel = null;
-        foreach (Versions::CHANNELS as $channel) {
+        foreach (Versions::$channels as $channel) {
             if ($input->getOption($channel)) {
                 $requestedChannel = $channel;
                 $versionsUtil->setChannel($channel);

src/Composer/SelfUpdate/Versions.php

@@ -21,7 +21,7 @@ use Composer\Json\JsonFile;
  */
 class Versions
 {
-    const CHANNELS = array('stable', 'preview', 'snapshot', '1', '2');
+    public static $channels = array('stable', 'preview', 'snapshot', '1', '2');
 
     private $rfs;
     private $config;
@@ -52,8 +52,8 @@ class Versions
 
     public function setChannel($channel)
     {
-        if (!in_array($channel, self::CHANNELS, true)) {
-            throw new \InvalidArgumentException('Invalid channel '.$channel.', must be one of: ' . implode(', ', self::CHANNELS));
+        if (!in_array($channel, self::$channels, true)) {
+            throw new \InvalidArgumentException('Invalid channel '.$channel.', must be one of: ' . implode(', ', self::$channels));
         }
 
         $channelFile = $this->config->get('home').'/update-channel';