PHP缺少apc模块导致Composer没有任何输出

在一台服务器上部署代码的时候发现使用composer没有任何输出，该想的办法都想了，还是没有找到原因，于是查看composer.phar，发现如下代码：

<?php
/*
 * This file is part of Composer.
 *
 * (c) Nils Adermann <naderman@naderman.de>
 *     Jordi Boggiano <j.boggiano@seld.be>
 *
 * For the full copyright and license information, please view
 * the license that is located at the bottom of this file.
 */

// Avoid APC causing random fatal errors per https://github.com/composer/composer/issues/264
if (extension_loaded('apc') && ini_get('apc.enable_cli') && ini_get('apc.cache_by_default')) {
    if (version_compare(phpversion('apc'), '3.0.12', '>=')) {
        ini_set('apc.cache_by_default', 0);
    } else {
        fwrite(STDERR, 'Warning: APC <= 3.0.12 may cause fatal errors when running composer commands.'.PHP_EOL);
        fwrite(STDERR, 'Update APC, or set apc.enable_cli or apc.cache_by_default to 0 in your php.ini.'.PHP_EOL);
    }
}

Phar::mapPhar('composer.phar');
require 'phar://composer.phar/bin/composer';

__HALT_COMPILER(); ?>

于是检查PHP是否缺少apc模块，果然没有安装apc模块，安装之后一切恢复正常。