The PHP 4 documentation was removed from the PHP Manual in August 2014, approximately six years after PHP 4 reached its end of life. However, we have provided downloadable copies of the manual for anyone who would need it.
An attempt has been made to preserve as much documentation related to PHP 4, as possible. Despite this, we don't have a nice, separate manual covering only PHP 4. The reason for this is how our documentation is structured. Even so, the archived copy describes more aspects of PHP 4 than actual manual described in August 2014 (e.g. it covers more PHP 4 extensions).
To download a copy of the manual for PHP 4, see the documentation archives. Please, remember, that archived version should not be used in everyday development, unless you are developing PHP 4 applications. This version lacks many topics connected with PHP 5 and it is not updated anymore.