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Syntax

To practice some basic PHP skills, let's piggy-back on the hello-world example application set up in Week 2.

For this note set, create a new file at hello-world/syntax.php and paste in the following code:

<?php
$temperature = 75;
$scale = 'F';
$location = "Cambridge";

echo 'Temperature in '.$location.': '.$temperature.' '.$scale;
?>

Load this file in your browser via your local server (http://hello-world.loc/syntax.php); it should look like this:

Basics PHP page loaded in the browser

Study each line of the example and note that it sets 3 variables (an Integer and two Strings):

$temperature = 75;
$scale = "F";
$location = 'Cambridge';

...and outputs a String using the echo construct:

echo 'Temperature in '.$location.': '.$temperature.' '.$scale;

Additional observations:

  • PHP code is surrounded by a start PHP tag <?php and an end PHP tag ?>.
  • PHP statements end with a semi-colon.
  • Variables are indicated with a $ sign.
  • Values are assigned to variables using the assignment operator = (equal sign).
  • Strings can be surrounded in single ('F') or double quotes ("Cambridge").
  • Values can be joined together using the concatenation operator . (period).

View Source

Use your browser's View Source feature to look at the underlying source code your browser processes. Note how you don't see the PHP code since it's processed on the server rather than the browser; you only see any resulting output.

View source of the basics example

Comments

PHP supports the following comment styles:

<?php

// This is a one-line c++ style comment
echo 'This is a test';

/* This is a multi line comment
   yet another line of comment */

echo 'This is yet another test';

# This is a one-line shell-style comment
echo 'One Final Test';

?>

And these styles can be used to organize and comment your code in various ways:

<?php
//=====================================================
// CATEGORY LARGE FONT
//=====================================================

//-----------------------------------------------------
// Sub-Category Smaller Font
//-----------------------------------------------------

/* Title Here Notice the First Letters are Capitalized */

# Option 1
# Option 2
# Option 3

/*
* This is a detailed explanation
* of something that should require
* several paragraphs of information.
*/

// This is a single line quote.
?>

Your comment styling is up to you— just aim for consistency.

A note on PHP tags in upcoming examples

From this point forward, example PHP code will be shown without PHP start/end tags for the sake of brevity.

I.e., instead of this:

<?php
echo 'Hello World';
?>

You'll see this:

echo 'Hello World';

The only exception to this is the note set on mixing PHP and HTML where PHP start/end tags will be used to distinguish from HTML code.