With ‘upgrade.php‘ on-hand, you can use many features from newer PHP versions (up to 5.3/5.4 currently) without losing compatibility to older interpreters and outdated webserver setups. It takes care of emulating any functions (with their original names) that are missing at runtime.
You just include() it into your application. Then you’re freed from micromanaging backwards compliance and wasting time with workarounds. Simply use the more featureful PHP functions.
Following functions are currently emulated:
gzdecode · hex2bin · class_uses · zlib_encode · zlib_decode · session_status · http_response_code · http_redirect · http_send_content_type · json_encode · json_decode · preg_filter · lcfirst · array_replace · strptime · error_get_last · preg_last_error · lchown · lchgrp · ob_get_headers · xmlentities · stripos · strripos · str_ireplace · get_headers · headers_list · fprintf · vfprintf · str_split · http_build_query · convert_uuencode · convert_uudecode · scandir · idate · time_nanosleep · strpbrk · php_real_logo_guid · php_egg_logo_guid · php_strip_whitespace · php_check_syntax · get_declared_interfaces · array_combine · array_walk_recursive · substr_compare · spl_classes · class_parents · session_commit · dns_check_record · dns_get_mx · setrawcookie · file_put_contents · file_get_contents · fnmatch · glob · array_key_exists · array_intersect_assoc · array_diff_assoc · html_entity_decode · str_word_count · str_shuffle · get_include_path · set_include_path · restore_include_path · str_rot13 · array_change_key_case · array_fill · array_chunk · md5_file · is_a · fmod · floatval · is_infinite · is_nan · is_finite · var_export · strcoll · diskfreespace · disktotalspace · vprintf · vsprintf · import_request_variables · hypot · log1p · expm1 · sinh · cosh · tanh · asinh · acosh · atanh · array_udiff_uassoc · array_udiff_assoc · array_diff_uassoc · array_udiff · array_uintersect_uassoc · array_uintersect_assoc · array_uintersect · array_intersect_uassoc · mime_content_type · image_type_to_mime_type · image_type_to_extension · exif_imagetype · array_filter · array_map · is_callable · array_search · array_reduce · is_scalar · localeconv · call_user_func_array · call_user_method_array · array_sum · constant · is_null · pathinfo · escapeshellarg · is_uploaded_file · move_uploaded_file · strncasecmp · wordwrap · php_uname · php_sapi_name