Auto-disable misbehaving curl downloader on php 5, refs #9002

src/Composer/Util/HttpDownloader.php

@@ -80,7 +80,27 @@ class HttpDownloader
         list($job) = $this->addJob(array('url' => $url, 'options' => $options, 'copyTo' => false), true);
         $this->wait($job['id']);
 
-        return $this->getResponse($job['id']);
+        $response = $this->getResponse($job['id']);
+
+        // check for failed curl response (empty body but successful looking response)
+        if (
+            $this->curl
+            && PHP_VERSION_ID < 70000
+            && $response->getBody() === null
+            && $response->getStatusCode() === 200
+            && $response->getHeader('content-length') !== '0'
+        ) {
+            $this->io->writeError('<warning>cURL downloader failed to return a response, disabling it and proceeding in slow mode.</warning>');
+
+            $this->curl = null;
+
+            list($job) = $this->addJob(array('url' => $url, 'options' => $options, 'copyTo' => false), true);
+            $this->wait($job['id']);
+
+            $response = $this->getResponse($job['id']);
+        }
+
+        return $response;
     }
 
     public function add($url, $options = array())