Installing/Configuring
PHP Manual

Installation

This » PECL extension is not bundled with PHP.

An example installation procedure on Ubuntu 18.04 with PHP 7.2: 

// Dependencies
$ apt install build-essential libprotobuf-dev libboost-dev openssl protobuf-compiler liblz4-tool zstd

// PHP with the desired extensions; php7.2-dev is required to compile
$ apt install php7.2-cli php7.2-dev php7.2-mysql php7.2-pdo php7.2-xml

// Compile the extension
$ pecl install mysql_xdevapi

The pecl install command does not enable PHP extensions (by default) and enabling PHP extensions can be done in several ways. Another PHP 7.2 on Ubuntu 18.04 example: 

// Create its own ini file
$ echo "extension=mysql_xdevapi.so" > /etc/php/7.2/mods-available/mysql_xdevapi.ini

// Use the 'phpenmod' command (note: it's Debian/Ubuntu specific)
$ phpenmod -v 7.2 -s ALL mysql_xdevapi

// A 'phpenmod' alternative is to manually symlink it
// $ ln -s /etc/php/7.2/mods-available/mysql_xdevapi.ini /etc/php/7.2/cli/conf.d/20-mysql_xdevapi.ini

// Let's see which MySQL extensions are enabled now
$ php -m |grep mysql

mysql_xdevapi
mysqli
mysqlnd
pdo_mysql

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/mysql_xdevapi.