What for PHP_ZTS is a predefined constant in PHP?

Question

There is a predefined constant PHP_ZTS available from PHP 5.2.7, but there is no documentation in the manual.

Can anyone explain what his purpose is?

Answer 1

PHP_ZTS is a predefined constant that returns whether the Zend Thread Safety (ZTS) function is enabled.

PHP_ZTS (return value "0" (false) indicates that compiled php is not safe)

Some extensions require ZTS to work with PHP ; he allowed the use of the option:

 --enable-maintainer-zts 

at PHP build time.