Sets the value of the given configuration option. Returns the old value on success, FALSE on failure. The configuration option will keep this new value during the script's execution, and will be restored at the script's ending.
Not all the available options can be changed using ini_set(). Below is a table with a list of all PHP options (as of PHP 4.0.5-dev), indicating which ones can be changed/set and at what level.
Table 1. Configuration options
| Name | Default | Changeable |
|---|---|---|
| define_syslog_variables | "0" | PHP_INI_ALL |
| highlight.bg | HL_BG_COLOR | PHP_INI_ALL |
| highlight.comment | HL_COMMENT_COLOR | PHP_INI_ALL |
| highlight.default | HL_DEFAULT_COLOR | PHP_INI_ALL |
| highlight.html | HL_HTML_COLOR | PHP_INI_ALL |
| highlight.keyword | HL_KEYWORD_COLOR | PHP_INI_ALL |
| highlight.string | HL_STRING_COLOR | PHP_INI_ALL |
| allow_call_time_pass_reference | "1" | PHP_INI_SYSTEM|PHP_INI_PERDIR |
| asp_tags | "0" | PHP_INI_SYSTEM|PHP_INI_PERDIR |
| display_errors | "1" | PHP_INI_ALL |
| display_startup_errors | "0" | PHP_INI_ALL |
| enable_dl | "1" | PHP_INI_SYSTEM |
| error_append_string | NULL | PHP_INI_ALL |
| error_prepend_string | NULL | PHP_INI_ALL |
| expose_php | "1" | PHP_INI_SYSTEM |
| html_errors | "1" | PHP_INI_SYSTEM |
| ignore_user_abort | "0" | PHP_INI_ALL |
| implicit_flush | "0" | PHP_INI_PERDIR|PHP_INI_SYSTEM |
| log_errors | "0" | PHP_INI_ALL |
| magic_quotes_gpc | "1" | PHP_INI_PERDIR|PHP_INI_SYSTEM |
| magic_quotes_runtime | "0" | PHP_INI_ALL |
| magic_quotes_sybase | "0" | PHP_INI_PERDIR|PHP_INI_SYSTEM |
| output_buffering | "0" | PHP_INI_PERDIR|PHP_INI_SYSTEM |
| output_handler | NULL | PHP_INI_PERDIR|PHP_INI_SYSTEM |
| register_argc_argv | "1" | PHP_INI_ALL |
| register_globals | "1" | PHP_INI_PERDIR|PHP_INI_SYSTEM |
| safe_mode | "0" | PHP_INI_SYSTEM |
| short_open_tag | "1" | PHP_INI_SYSTEM|PHP_INI_PERDIR |
| sql.safe_mode | "0" | PHP_INI_SYSTEM |
| track_errors | "0" | PHP_INI_ALL |
| y2k_compliance | "0" | PHP_INI_ALL |
| arg_separator | "&" | PHP_INI_ALL |
| auto_append_file | NULL | PHP_INI_ALL |
| auto_prepend_file | NULL | PHP_INI_ALL |
| doc_root | NULL | PHP_INI_SYSTEM |
| default_charset | SAPI_DEFAULT_CHARSET | PHP_INI_ALL |
| default_mimetype | SAPI_DEFAULT_MIMETYPE | PHP_INI_ALL |
| error_log | NULL | PHP_INI_ALL |
| extension_dir | PHP_EXTENSION_DIR | PHP_INI_SYSTEM |
| gpc_order | "GPC" | PHP_INI_ALL |
| include_path | PHP_INCLUDE_PATH | PHP_INI_ALL |
| max_execution_time | "30" | PHP_INI_ALL |
| open_basedir | NULL | PHP_INI_SYSTEM |
| safe_mode_exec_dir | "1" | PHP_INI_SYSTEM |
| upload_max_filesize | "2M" | PHP_INI_ALL |
| file_uploads | "1" | PHP_INI_ALL |
| post_max_size | "8M" | PHP_INI_SYSTEM |
| upload_tmp_dir | NULL | PHP_INI_SYSTEM |
| user_dir | NULL | PHP_INI_SYSTEM |
| variables_order | NULL | PHP_INI_ALL |
| SMTP | "localhost" | PHP_INI_ALL |
| browscap | NULL | PHP_INI_SYSTEM |
| error_reporting | NULL | PHP_INI_ALL |
| memory_limit | "8M" | PHP_INI_ALL |
| precision | "14" | PHP_INI_ALL |
| sendmail_from | NULL | PHP_INI_ALL |
| sendmail_path | DEFAULT_SENDMAIL_PATH | PHP_INI_SYSTEM |
| disable_functions | "" | PHP_INI_SYSTEM |
| allow_url_fopen | "1" | PHP_INI_ALL |
Table 2. Definition of PHP_INI_* constants
| Constant | Value | Meaning |
|---|---|---|
| PHP_INI_USER | 1 | Entry can be set in user scripts |
| PHP_INI_PERDIR | 2 | Entry can be set in .htaccess |
| PHP_INI_SYSTEM | 4 | Entry can be set in php.ini or httpd.conf |
| PHP_INI_ALL | 7 | Entry can be set anywhere |
See also ini_alter(), ini_get(), ini_restore()