PHP 8.2环境下Symfony/Composer出现弃用错误

问题 #

CentOS开发环境刚把PHP升级到8.2.10，尝试安装最新版mPDF时，执行composer require mpdf/mpdf出现一堆Symfony相关的弃用错误，同时系统提示不要用root身份运行Composer。当前Composer版本是2.1.3，本人擅长开发但运维不熟，求解决。

具体错误信息：

$ composer require mpdf/mpdf

Deprecated: Return type of Symfony\Component\Console\Helper\HelperSet::getIterator() should either be compatible with IteratorAggregate::getIterator(): Traversable, or the #[\ReturnTypeWillChange] attribute should be used to temporarily suppress the notice in /usr/share/php/Symfony3/Component/Console/Helper/HelperSet.php on line 104
Deprecation Notice: strlen(): Passing null to parameter #1 ($string) of type string is deprecated in /usr/share/php/JsonSchema5/Constraints/Constraint.php:48
Deprecation Notice: Return type of Symfony\Component\Process\Process::getIterator($flags = 0) should either be compatible with IteratorAggregate::getIterator(): Traversable, or the #[\ReturnTypeWillChange] attribute should be used to temporarily suppress the notice in /usr/share/php/Symfony3/Component/Process/Process.php:567
Deprecation Notice: Return type of Composer\Repository\ArrayRepository::count() should either be compatible with Countable::count(): int, or the #[\ReturnTypeWillChange] attribute should be used to temporarily suppress the notice in /usr/share/php/Composer/Repository/ArrayRepository.php:286
Deprecation Notice: Return type of Composer\Repository\ArrayRepository::count() should either be compatible with Countable::count(): int, or the #[\ReturnTypeWillChange] attribute should be used to temporarily suppress the notice in /usr/share/php/Composer/Repository/ArrayRepository.php:286
Deprecation Notice: Return type of Composer\Repository\ArrayRepository::count() should either be compatible with Countable::count(): int, or the #[\ReturnTypeWillChange] attribute should be used to temporarily suppress the notice in /usr/share/php/Composer/Repository/ArrayRepository.php:286
Deprecation Notice: Using ${var} in strings is deprecated, use {$var} instead in /usr/share/php/Composer/Autoload/AutoloadGenerator.php:799
Deprecation Notice: Using ${var} in strings is deprecated, use {$var} instead in /usr/share/php/Composer/Autoload/AutoloadGenerator.php:804
Do not run Composer as root/super user! See https://getcomposer.org/root for details

执行composer --version时也出现相同弃用错误：

$ composer --version

Deprecated: Return type of Symfony\Component\Console\Helper\HelperSet::getIterator() should either be compatible with IteratorAggregate::getIterator(): Traversable, or the #[\ReturnTypeWillChange] attribute should be used to temporarily suppress the notice in /usr/share/php/Symfony3/Component/Console/Helper/HelperSet.php on line 104
Deprecation Notice: strlen(): Passing null to parameter #1 ($string) of type string is deprecated in /usr/share/php/JsonSchema5/Constraints/Constraint.php:48
Deprecation Notice: Return type of Symfony\Component\Process\Process::getIterator($flags = 0) should either be compatible with IteratorAggregate::getIterator(): Traversable, or the #[\ReturnTypeWillChange] attribute should be used to temporarily suppress the notice in /usr/share/php/Symfony3/Component/Process/Process.php:567
Deprecation Notice: Return type of Composer\Repository\ArrayRepository::count() should either be compatible with Countable::count(): int, or the #[\ReturnTypeWillChange] attribute should be used to temporarily suppress the notice in /usr/share/php/Composer/Repository/ArrayRepository.php:286
Deprecation Notice: Return type of Composer\Repository\ArrayRepository::count() should either be compatible with Countable::count(): int, or the #[\ReturnTypeWillChange] attribute should be used to temporarily suppress the notice in /usr/share/php/Composer/Repository/ArrayRepository.php:286
Deprecation Notice: Return type of Composer\Repository\ArrayRepository::count() should either be compatible with Countable::count(): int, or the #[\ReturnTypeWillChange] attribute should be used to temporarily suppress the notice in /usr/share/php/Composer/Repository/ArrayRepository.php:286
Deprecation Notice: Using ${var} in strings is deprecated, use {$var} instead in /usr/share/php/Composer/Autoload/AutoloadGenerator.php:799
Deprecation Notice: Using ${var} in strings is deprecated, use {$var} instead in /usr/share/php/Composer/Autoload/AutoloadGenerator.php:804
Do not run Composer as root/super user! See https://getcomposer.org/root for details
Continue as root/super user [yes]?
Composer 2.1.3 2021-06-09 16:31:20

解决方案 #

• 升级Composer版本：你的Composer 2.1.3是2021年的旧版本，完全不兼容PHP 8.2。执行以下命令升级：

  composer self-update
  

  如果当前是root用户，可加--no-plugins参数避免冲突：

  composer self-update --no-plugins
  

  升级后，Composer会更新自身依赖的Symfony组件，那些弃用提示会自动消失。

• 不要以root身份运行Composer：

  1. 创建普通用户（如果没有）：

     useradd -m devuser
     passwd devuser
     

  2. 给项目目录赋予devuser权限：

     chown -R devuser:devuser /path/to/your/project
     

  3. 切换到devuser执行Composer命令：

     su - devuser
     cd /path/to/your/project
     composer require mpdf/mpdf
     

  这样既符合安全规范，也能避免权限相关的潜在问题。

• 验证修复效果：升级完成后，执行composer --version，如果不再出现弃用提示，说明问题解决，再重新执行mPDF的安装命令即可。

内容的提问来源于stack exchange，提问作者abe1432181