Turning off the UART functioning as a serial console

See the instructions here.

Setup Permission

You can determine the user PHP is running as with this command in a php page:

<?php
echo exec('whoami');
?>

It will typcially be 'www-data'.  All serial connections, virtual or physical, are owned by the 'dialout' group so if you add www-data to the dialout group your PHP scripts will be able to open/read/write the UART (or other serial devices). The following command will add the group to www-data.

usermod -a -G dialout www-data

You can confirm this with:

groups www-data

You now need to restart the RPi for the setting to take effect.

Transmit A String

<?php
	echo system("echo \"hello\" > /dev/ttyAMA0 ");
?>

Include this in a php page, load the page using a browser and you should see the data being sent out of the UART TX pin.

If you want to include variables:

		//Set baud rate
		system("stty -F /dev/ttyAMA0 57600");
		
		//Send string including variables
		system("sudo echo \"Hello the value is: " . (string)$some_int_variable . "and also: " . escapeshellarg($some_string_variable) .	"\" > /dev/ttyAMA0");