How can I execute a PHP script using command line?

In command line run the following: php -a ;This will open interactive shell for php which can be used to write your script and run it immediately.
php -f yourScriptFile.php ; This will run the php script in your script file and return the output of execution.
php -r $PHPScript ; This used as run-as-you-type PHP, which is really useful for checking little snippets.