These are the Zend Optimizer codes for respective PHP versions. Paste these codes at the end of php.ini file.

For PHP 7.0, 7.1, 7.2, 7.3 and 7.4, add one of the following Zend Extensions at end of of php.ini:
​zend_extension = /usr/local/lib/ioncube/php7.0/ioncube/ioncube_loader_lin_7.0.so
zend_extension = /usr/local/lib/ioncube/php7.1/ioncube/ioncube_loader_lin_7.1.so
zend_extension = /usr/local/lib/ioncube/php7.2/ioncube/ioncube_loader_lin_7.2.so
zend_extension = /usr/local/lib/ioncube/php7.3/ioncube/ioncube_loader_lin_7.3.so
zend_extension = /usr/local/lib/ioncube/php7.4/ioncube/ioncube_loader_lin_7.4.so

PHP 5.6:
[Zend]
zend_extension = /usr/local/lib/ioncube/php5.6/ioncube/ioncube_loader_lin_5.6.so
zend_extension = /usr/local/lib/zend/php5.6/ZendGuardLoader.so

​PHP 5.5:
[Zend]
zend_extension = /usr/local/lib/ioncube/php5.5/ioncube/ioncube_loader_lin_5.5.so
zend_extension = /usr/local/lib/zend/php5.5/ZendGuardLoader.so

PHP 5.4:
[Zend]
zend_extension = /usr/local/lib/ioncube/php5.4/ioncube/ioncube_loader_lin_5.4.so
zend_extension = /usr/local/lib/zend/php5.4/ZendGuardLoader.so

PHP 5.3
[Zend]
zend_extension = /usr/local/lib/ioncube/php5.3/ioncube/ioncube_loader_lin_5.3.so
zend_extension = /usr/local/lib/zend/php5.3/ZendGuardLoader.so