How to install and run phpize

Ohk.. I got it running by typing /usr/bin/phpize instead of only phpize.

For recent versions of Debian/Ubuntu (Debian 9+ or Ubuntu 16.04+) install the php-dev dependency package, which will automatically install the correct version of php{x}-dev for your distribution:

sudo apt install php-dev

Older versions of Debian/Ubuntu:

For PHP 5, it's in the php5-dev package.

sudo apt-get install php5-dev

For PHP 7.x (from rahilwazir comment):

sudo apt-get install php7.x-dev

RHEL/CentOS/yum

yum install php-devel # see comments

For PHP7 Users

7.1

sudo apt install php7.1-dev

7.2

sudo apt install php7.2-dev

7.3

sudo apt install php7.3-dev

7.4

sudo apt install php7.4-dev

If not sure about your PHP version, simply run command php -v