PHP Manual: Differences to other SAPIs

Unlike the CGI SAPI, no headers are written to the output.

Though the CGI SAPI provides a way to suppress HTTP headers, there's no equivalent switch to enable them in the CLI SAPI.

CLI is started up in quiet mode by default, though the -q and --no-header switches are kept for compatibility so that it is possible to use older CGI scripts.

It does not change the working directory to that of the script. (-C and --no-chdir switches kept for compatibility)

Plain text error messages (no HTML formatting).

There are certain php.ini directives which are overridden by the CLI SAPI because they do not make sense in shell environments:

**Overridden `php.ini` directives**
Directive	CLI SAPI default value	Comment
html_errors	`false`	Defaults to `false`, as it can be quite hard to read error messages in the shell environment when they are cluttered up with uninterpreted HTML tags.
implicit_flush	`true`	In a shell environment, it is usually desirable for output, such as from print, echo and friends, to be displayed immediately, and not held in a buffer. Nonetheless, it is still possible to use output buffering to defer or manipulate standard output.
max_execution_time	0 (unlimited)	PHP in a shell environment tends to be used for a much more diverse range of purposes than typical Web-based scripts, and as these can be very long-running, the maximum execution time is set to unlimited.
register_argc_argv	`true`	Setting this to `true` means that scripts executed via the CLI SAPI always have access to argc (number of arguments passed to the application) and argv (array of the actual arguments). The PHP variables `$argc` and `$argv` are automatically set to the appropriate values when using the CLI SAPI. These values can also be found in the `$_SERVER` array, for example: `$_SERVER['argv']`.
output_buffering	`false`	Although the `php.ini` setting is hardcoded to `false`, the Output buffering functions are available.
max_input_time	`false`	The PHP CLI does not support GET, POST or file uploads.

Note:
These directives cannot be initialized with another value from the configuration file php.ini or a custom one (if specified). This limitation is because the values are applied after all configuration files have been parsed. However, their values can be changed during runtime (although this is not sensible for all of them, such as register_argc_argv).

Note:
It is recommended to set ignore_user_abort for command line scripts. See ignore_user_abort for more information.

To ease working in the shell environment, a number of constants are defined for I/O streams .

The CLI SAPI does not change the current directory to the directory of the executed script.

Example #1 Example showing the difference to the CGI SAPI:

<?php
// Our simple test application named test.php
echo getcwd(), "\n";
?>

When using the CGI version, the output is:

$ pwd
/tmp

$ php -q another_directory/test.php
/tmp/another_directory

This clearly shows that PHP changes its current directory to the one of the executed script.

Using the CLI SAPI yields:

$ pwd
/tmp

$ php -f another_directory/test.php
/tmp

This allows greater flexibility when writing shell tools in PHP.

Note:
The CGI SAPI supports this CLI SAPI behaviour by means of the -C switch when run from the command line.