For more advanced users, there is one more way to take advantage of PHP for console programming: passing code directly to the PHP CLI binary.
Through the use of the -r argument, it becomes possible to enter PHP code on the command line. The opening and closing PHP tags are not required, as the -r tag is designed to execute pure PHP code.
Here is a very basic example of -r usage:
php -r 'phpinfo();'
As you can see, you get the PHP module information printed straight to the console. However, it is a very basic example, and does not highlight the key problem of sending code direct to PHP with the -r argument.
The problem, which may cause many headaches because of it is elusive nature, is that many shells (I use bash, which is "affected"), have variables of their own, and, if you use double quotes, will perform variable substitution even before PHP gets hold of the code. As a result, this seemingly innocuous code will fail:
php -r "$abc = 'def';"
Bash, and many other shells, will evaluate $foo and find it unset, and will pass a blank on to PHP. Therefore, what PHP will see is this:
The solution to the problem, as I mentioned already, is to use single quotes with -r. However, you will need to constantly be on guard when using backslashes for escaping, or, even harder, trying to get shell variables in your code.