Sets the value of the given configuration option. Returns the old value on success, false on failure.
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_ALL |
| magic_quotes_runtime | "0" | PHP_INI_ALL |
| magic_quotes_sybase | "0" | PHP_INI_ALL |
| 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_ALL |
| 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()