从5.6更新到7之后，Symfony 3引发了这个异常：
致命错误：类 Symfony的\分量\ HttpFoundation \会议\存储\代理\ SessionHandlerProxy 包含1个抽象方法，因此必须声明为abstract或 实现其余的方法（SessionHandlerInterface :: write） \供应商\ symfony的\ symfony中的\ src \的Symfony \分量\ HttpFoundation \会议\存储\代理\ SessionHandlerProxy.php 第19行
Symfony 3与PHP 7不兼容吗？相同的代码适用于php 5.6
composer show -i output：
doctrine/annotations v1.2.7 Docblock Annotations Parser
doctrine/cache v1.6.0 Caching library offering an o...
doctrine/collections v1.3.0 Collections Abstraction library
doctrine/common v2.6.1 Common Library for Doctrine p...
doctrine/dbal v2.5.3 Database Abstraction Layer
doctrine/doctrine-bundle 1.6.1 Symfony DoctrineBundle
doctrine/doctrine-cache-bundle 1.2.2 Symfony Bundle for Doctrine C...
doctrine/inflector v1.1.0 Common String Manipulations w...
doctrine/instantiator 1.0.5 A small, lightweight utility ...
doctrine/lexer v1.0.1 Base library for a lexer that...
doctrine/orm v2.5.3 Object-Relational-Mapper for PHP
incenteev/composer-parameter-handler v2.1.2 Composer script handling your...
jdorn/sql-formatter v1.2.17 a PHP SQL highlighting library
kriswallsmith/assetic v1.3.2 Asset Management for PHP
monolog/monolog 1.17.2 Sends your logs to files, soc...
paragonie/random_compat v1.2.2 PHP 5.x polyfill for random_b...
psr/log 1.0.0 Common interface for logging ...
sensio/distribution-bundle v5.0.3 Base bundle for Symfony Distr...
sensio/framework-extra-bundle v3.0.12 This bundle provides a way to...
sensio/generator-bundle v3.0.3 This bundle generates code fo...
sensiolabs/security-checker v3.0.2 A security checker for your c...
swiftmailer/swiftmailer v5.4.1 Swiftmailer, free feature-ric...
symfony/assetic-bundle v2.7.1 Integrates Assetic into Symfony2
symfony/monolog-bundle v2.8.2 Symfony MonologBundle
symfony/phpunit-bridge v2.8.1 Symfony PHPUnit Bridge
symfony/polyfill-intl-icu v1.1.1 Symfony polyfill for intl's I...
symfony/polyfill-mbstring v1.1.1 Symfony polyfill for the Mbst...
symfony/polyfill-php56 v1.1.1 Symfony polyfill backporting ...
symfony/polyfill-php70 v1.1.1 Symfony polyfill backporting ...
symfony/polyfill-util v1.1.1 Symfony utilities for portabi...
symfony/swiftmailer-bundle v2.3.9 Symfony SwiftmailerBundle
symfony/symfony v3.0.3 The Symfony PHP framework
twig/twig v1.24.0 Twig, the flexible, fast, and...
的php.ini
[opcache]
opcache.enable=1
opcache.memory_consumption=128
opcache.interned_strings_buffer=16
opcache.max_accelerated_files=6000
opcache.use_cwd=1
opcache.validate_timestamps=1
opcache.save_comments=1
opcache.fast_shutdown=1
答案 0 :(得分：12)
重新启动httpd服务可以清除此错误。
在遇到错误之后无法重现错误，但它可能是PHP崩溃，反过来导致不完整的状态，使错误消息卡在httpd服务的缓冲区响应中，然后为每个服务器提供服务从那时起对该服务上提供的任何虚拟主机的单一请求，直到该服务被终止。
信用 Scott Flacks 在另一个答案中发表评论。
答案 1 :(得分：0)
尝试升级到Symfony 3.1。
Symfony 3.0于2015年11月发布，虽然它should be compatible with PHP7 - PHP7于2015年12月正式发布，。