even though the manual says the json extension is enabled by default and compiled into the core, I had to do a "yum install php-json" on centos 8 running php 7.2
JSON 扩展默认内置并编译进了 PHP。
自 PHP 8.0.0 起，JSON 扩展是核心 PHP 扩展，所以始终启用。
安装此 PECL 扩展相关的信息可在手册中标题为 PECL 扩展的安装章节中找到。更多信息如新的发行版本、下载、源文件、 维护人员信息及变更日志等，都在此处： » https://pecl.php.net/package/json
even though the manual says the json extension is enabled by default and compiled into the core, I had to do a "yum install php-json" on centos 8 running php 7.2On Ubuntu 13.10 you have to install this extension first (PHP 5.5.3):
apt-get install php5-json
(Don't forget to restart web server.)