Sanitize prefix

src/Composer/Autoload/AutoloadGenerator.php

@@ -858,9 +858,9 @@ CLASSMAPAUTHORITATIVE;
         }
 
         if ($this->apcu) {
-            $apcuPrefix = is_string($this->apcu) ? $this->apcu : substr(base64_encode(md5(uniqid('', true), true)), 0, -3);
+            $apcuPrefix = var_export(is_string($this->apcu) ? $this->apcu : substr(base64_encode(md5(uniqid('', true), true)), 0, -3), true);
             $file .= <<<APCU
-        \$loader->setApcuPrefix('$apcuPrefix');
+        \$loader->setApcuPrefix($apcuPrefix);
 
 APCU;
         }

tests/Composer/Test/Autoload/AutoloadGeneratorTest.php

@@ -853,7 +853,7 @@ EOF;
         file_put_contents($this->vendorDir.'/c/c/foo/ClassMapBaz.php', '<?php class ClassMapBaz {}');
 
         $this->generator->setClassMapAuthoritative(true);
-        $this->generator->setApcu('customPrefix');
+        $this->generator->setApcu('custom\'Prefix');
         $this->generator->dump($this->config, $this->repository, $package, $this->im, 'composer', false, '_7');
 
         $this->assertFileExists($this->vendorDir.'/composer/autoload_classmap.php', "ClassMap file needs to be generated.");
@@ -869,7 +869,7 @@ EOF;
         $this->assertAutoloadFiles('classmap8', $this->vendorDir.'/composer', 'classmap');
 
         $this->assertStringContainsString('$loader->setClassMapAuthoritative(true);', file_get_contents($this->vendorDir.'/composer/autoload_real.php'));
-        $this->assertStringContainsString('$loader->setApcuPrefix(\'customPrefix\');', file_get_contents($this->vendorDir.'/composer/autoload_real.php'));
+        $this->assertStringContainsString('$loader->setApcuPrefix(\'custom\\\'Prefix\');', file_get_contents($this->vendorDir.'/composer/autoload_real.php'));
     }
 
     public function testFilesAutoloadGeneration()