/usr/share/php/Symfony/Component/Serializer/Encoder/ is in php-symfony-serializer 3.4.6+dfsg-1.
This file is owned by root:root, with mode 0o755.
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/usr/share/php/Symfony/Component/Serializer/Encoder/ChainDecoder.php
/usr/share/php/Symfony/Component/Serializer/Encoder/ChainEncoder.php
/usr/share/php/Symfony/Component/Serializer/Encoder/ContextAwareDecoderInterface.php
/usr/share/php/Symfony/Component/Serializer/Encoder/ContextAwareEncoderInterface.php
/usr/share/php/Symfony/Component/Serializer/Encoder/CsvEncoder.php
/usr/share/php/Symfony/Component/Serializer/Encoder/DecoderInterface.php
/usr/share/php/Symfony/Component/Serializer/Encoder/EncoderInterface.php
/usr/share/php/Symfony/Component/Serializer/Encoder/JsonDecode.php
/usr/share/php/Symfony/Component/Serializer/Encoder/JsonEncode.php
/usr/share/php/Symfony/Component/Serializer/Encoder/JsonEncoder.php
/usr/share/php/Symfony/Component/Serializer/Encoder/NormalizationAwareInterface.php
/usr/share/php/Symfony/Component/Serializer/Encoder/SerializerAwareEncoder.php
/usr/share/php/Symfony/Component/Serializer/Encoder/XmlEncoder.php
/usr/share/php/Symfony/Component/Serializer/Encoder/YamlEncoder.php