How to Check if php is running from cli (command line)

Php from command line

PHP scripts are usually opened in a web browser. But they can be run from command line or terminal as well. The syntax to run a script from commandline is very much similar to python or perl.

php /path/to/script/index.php

Inside a script it might be necessary to test if it is being run from command line or not. For example when a script is being from cron it might produce a different kind of output than when it is run from a browser url. In such cases the script needs to identify its running mode.

There are several ways to check if a php script is running from cli or not. Lets check them one by one

1. Check for the STDIN constant. STDIN is a constant that is defined when php is running from command line.

if(defined('STDIN') ) 
  echo("Running from CLI"); 
else 
  echo("Not Running from CLI");

However the above method has certain limitations. The test works very well when the script is being run using the php cli binary. In cronjobs for example a the command is specified as follows

php /path/to/script/index.php

Now the php command itself points to a php binary which can be either the php-cli binary or php-cgi binary. If it points to a php-cgi binary, like it happens on some hosting servers then the STDIN check will always be false. So the STDIN check method is not fully reliable. Lets take a look at another method for checking cli.

2. Check the php_sapi_name. The php_sapi_name function is supposed to return "cli" if the script is running from commandline.

if(php_sapi_name()==="cli")
  echo("Running from CLI"); 
else 
  echo("Not Running from CLI");

But this method too suffers the same problem as STDIN. It will work only if the cli mode has been triggered by the php cli binary. If php-cgi was used to initiate the script from the command line, it would always return "cgi-fcgi" for example.

3. Check the PHP_SAPI constant. The PHP_SAPI constant is the same as php_sapi_name function. So it has the same issues as mentioned above.

if (PHP_SAPI === 'cli')
  echo("Running from CLI"); 
else 
  echo("Not Running from CLI");

For cgi this approach can be useful :

if(stristr(PHP_SAPI , 'cgi') and getenv('TERM'))
  echo("Running from CLI"); 
else 
  echo("Not Running from CLI");

Working Solution

On servers that have fastcgi as the php handler for example, the php binary might point to php-cgi. So to test cli in an interface independant manner a different kind of check has to be done. Which is to check the contents of the $_SERVER variable for example.

function is_cli()
{
    if( empty($_SERVER['REMOTE_ADDR']) and !isset($_SERVER['HTTP_USER_AGENT']) and count($_SERVER['argv']) > 0) 
    {
        return true;
    } 
    return false;
}

The above method should properly detect cli in all cases. Can add an STDIN check too.

function is_cli()
{
	if( defined('STDIN') )
	{
		return true;
	}
	
	if( empty($_SERVER['REMOTE_ADDR']) and !isset($_SERVER['HTTP_USER_AGENT']) and count($_SERVER['argv']) > 0) 
	{
		return true;
	} 
	
	return false;
}

Looks neat. Try it.