Basic syntax

PHP script/code blocks

Open course/hello_world.php (a variant of the example on the Introduction page, but now "embedded" in our project)

<!doctype html>
<html lang="en">
<head>
    <?php include_once('../shared/meta.php') ?>
    <title>Hello world</title>
</head>
<body>
    <?php include_once('../shared/nav.php') ?>
    <main>
        <h1>Hello world</h1>
        <p><?php echo 'Hello world'; ?></p>
    </main>
    <?php include_once('../shared/footer.php') ?>
</body>
</html>

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Hello world

This file contains HTML tags and PHP script/code blocks
A PHP script/code block starts with <?php and ends with ?>
Every statement ends with a semicolon ;
The command echo is used to output text on the screen

REMARKS

If a PHP file only contains one (large) PHP script, the closing ?> may be omitted
```
<?php
...
```
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If a PHP script contains only one statement, the trailing ; may be omitted: both <?php echo 'Hello world' ?> and <?php echo 'Hello world'; ?> are correct
If a PHP script contains only one echo statement, you can use the shorthand <?= to open the PHP script block and execute the echo, as in <?= 'Hello world' ?>

Comments

Use // ... for single line comments or /* ... */ for multiple line comments

<?php
// This is a single line comment
    
/* This comment section
spans several
lines */
?>

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In PhpStorm you can use the shortcuts Ctrl+/ (single comment line) or Ctrl+Shift+/ (multiple comment lines)

Variables

Open course/variables.php

<div class="margin-3">
    <?php
    $student1 = 'John Doe';
    $percentage1 = 73.08;

    $student2 = 'Jane Smith';
    $percentage2 = 64.84;

    echo '<p>' . $student1 . ' graduates with ' . $percentage1 . ' %</p>' . "\n";
    echo "<p>$student2 graduates with $percentage2 %</p>\n";
    ?>
</div>

<div class="margin-3">
    <?php
    echo <<<RESULTS
        <p> $student1 graduates with $percentage1 %</p> 
        <p> $student2 graduates with $percentage2 %</p>          
    RESULTS;    
    ?>
</div>

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Variables

NAMING CONVENTIONS

All variables always start with a dollar sign $, followed by the name of the variable
Variable names start with a letter or _ (not a number!) and contain only alpha-numeric characters and _ (no spaces!)
Variable names are case-sensitive
Most PHP programmers use the camelCase or snake_case notation for variable names

Variables don't need to be declared (or given a data type) before giving them a value
The most important data types in PHP are
- numbers
  - 5, 3.14, 34e-2 (= 0.34), ...
  - without quotes
- strings
  - 'John Doe', "John", ...
  - enclosed in single ('...') or double quotes ("...")
- boolean values
  - true or false
- null
  - for variables without a value

Concatenation and interpolation

The concatenation operator . "concatenates" multiple strings and variables, as in '<p>' . $student1 . ' graduates with ' . $percentage1 . ' %</p>'
- Don't forget to add an extra space before/after a variable for a readable result
If you use double quotes ("<p>$student2 graduates with $percentage2 %</p>" ), the variables can be included in a single string as they are automatically interpolated

TIP

The HTML code that is generated by PHP is not formatted (no line breaks are inserted). To keep the HTML source code readable, it is advisable to add a newline character (\n) once in a while. This newline character should always be enclosed in double quotes ("...\n") .

Heredoc

A third syntax for strings is called the heredoc notation
- Very handy string syntax
  - No quotes and no "\n" are needed
  - Variables can be included/are interpolated
  - Emmet can be used
- Start with the <<< operator, after which an identifier (e.g. RESULTS) is provided
- The "string" itself starts on a new line
- The identifier is repeated (on a new line) to close the string

echo <<<RESULTS
    <p> $student1 graduates with $percentage1 %</p> 
    <p> $student2 graduates with $percentage2 %</p>          
RESULTS;

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# Basic syntax

# PHP script/code blocks

# Comments

# Variables

# Concatenation and interpolation

# Heredoc

Basic syntax

PHP script/code blocks

Comments

Variables

Concatenation and interpolation

Heredoc