How does PHP act when executed by a shell script? - php

Question

There is a PHP script I would like to execute by a cron-job but it has to be executed every seconds or every 2 seconds.
(PHP file updates the cover photo of a page via opengraph)
So I decided to write a shell script which is below. But how does php act when executed by a shell script, is it works normally like requested from a browser or what happens ?
Does sessions works ?
#!/bin/bash
while true; do
/path/to/file.php
sleep 1
done;
echo "Stopped" | mail -s "Cron script has stopped." mymail#domain.com

Answer 1

The difference is that you won't have $_GET, $_POST and other http specific stuff available. Sessions also won't work (why would you need them?). You obviously won't be able to set cookies, headers and other such things.
Other than that you can pretty much ignore the fact that you are "in a shell".
See here for more details: http://www.php.net/manual/en/features.commandline.differences.php

Answer 2

Take all the browser aspects away from PHP and that's how it'll act. You get no sessions (unless you were to call it with cURL and store the cookie somwehre).
You get no $_GET or $_POST - instead you need to use $args - but if you're not passing in any variables this isn't really relevant to you.
You'll obviously need to ensure that you've given your script execute permission, otherwise, call it using /path/to/php /path/to/file.php.
Take a look at these resources, they should help you out.
http://www.php.net/manual/en/features.commandline.differences.php
http://www.php.net/manual/en/features.commandline.php

Answer 3

When you execute php from the command line (CLI) you enter another environement.
There are multiple differences
Some of them are
Configuration
When executing from command line, you run another php.ini file. (Usually /etc/php5/php.ini)
Permissions
On the web, you usually execute PHP with www-data user.
When executing from command line, script will be executed as the current user.
Arguments
You do not have access to $_GET, $_POST, $_FILES... superglobals anymore.
Instead, you have new superglobals so as $argv and $argc
Sessions
You do not have access to session nor $_COOKIES
Relative Paths
The path that the script uses is relative from where the command started
So, careful when using relative ./ path in your script
Eg:
$ pwd
/path/to/project/
$ cat app/script.php
<?php
echo getcwd(), PHP_EOL;
$ php app/script.php
/path/to/project
$ cd app
$ php script.php
/path/to/project/app
You can get the current directory by using getcwd