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
The JSON extension is bundled and compiled into PHP by default.
As of PHP 8.0.0, the JSON extension is a core PHP extension, so it is always enabled.
Information for installing this PECL extension may be found in the manual chapter titled Installation of PECL extensions. Additional information such as new releases, downloads, source files, maintainer information, and a CHANGELOG, can be located here: » 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.)