In the tradition of our ancestors, let's start with a hello world program. All PHP files must start with a <?php tag unless it is for a html template. (We will learn about html templates later.)
There is a lot going on in this statement so let's work through it.
First, the echo keyword tells PHP to output some text.
Second, PHP stores text in strings.
To write a string, you surround letters with single or double quotes. The difference between single quoted strings and double quoted strings is that double quoted strings can hold special characters like \n which tells PHP to start a new line.
'I am a string';
"\nI am a string on a new line";
Third, all lines of code in PHP must end in a semi-colon.
echo "No semi-colon is a no-no\n";
Using semi-colons means we can write multiple statements on one line.
echo 'Hello'; echo " World\n";