PHP4

PHP4 module contains PHP5 functions which have been rewritten to make it compatible with PHP4.
Of course this module can't provide full support for PHP5, it's only defining the compatible functions.

You don't need to install this module, when you can install PEAR PHP_Compat instead.
Try:

pear install PHP_Compat-1.6.0a2

PHP_Compat Page: http://pear.php.net/package/PHP_Compat
If you can't do that, then install it.

Supported Functions

acosh() array_change_key_case() array_chunk() array_combine() array_diff_assoc() array_diff_key() array_diff_uassoc() array_diff_ukey() array_fill() array_intersect_assoc() array_intersect_key() array_intersect_uassoc() array_intersect_ukey() array_key_exists() array_product() array_search() array_slice() array_udiff() array_udiff_assoc() array_udiff_uassoc() array_uintersect() array_uintersect_assoc() array_uintersect_uassoc() array_walk_recursive() asinh() atanh() bcinvert() bcpowmod() call_user_func_array() constant() convert_uudecode() convert_uuencode() cosh() debug_print_backtrace() file_get_contents() file_put_contents() floatval() fprintf() fputcsv() getopt() get_headers() get_include_path() glob() htmlspecialchars() htmlspecialchars_decode() html_entity_decode() http_build_query() ibase_timefmt() idate() image_type_to_mime_type() inet_ntop() inet_pton() ini_get_all() is_a() is_callable() is_scalar() list.txt md5_file() mhash() microtime() mime_content_type() mkdir() ob_clean() ob_flush() ob_get_clean() ob_get_flush() pg_affected_rows() pg_escape_bytea() pg_unescape_bytea() php_ini_loaded_file() php_strip_whitespace() property_exists() range() restore_include_path() scandir() setcookie() setrawcookie() set_include_path() sinh() stripos() strpbrk() strripos() str_ireplace() str_rot13() str_shuffle() str_split() str_word_count() substr_compare() sys_get_temp_dir() tanh() time_sleep_until() var_export() version_compare() vprintf() vsprintf()

Can be used with following modules:
popups_reference #380932: setrawcookie is incompatible with PHP4

Not fully supported

Those function are defined (to prevent WSOD), but they can't be fully rewritten:

function error_get_last()

Compatible functions

Those function are defined using different function names, so you should update your code:

function parse_url_compat($url, $component=NULL) should be used instead of parse_url()

Could help with following modules:
path_redirect #448334: warning: parse_url() expects exactly 1 parameter, 2 given in path_redirect.module on line 341

Note

If you are using PHP_Compat, it's loading many files per each page refreshment. So please note that you should have some filesystem cache (like XCache, APC, etc.) to improve website performance.