PHP

Objectives

By the end of this lesson, developers will be able to:

• Explain what PHP is, and its role in web development
• List the four parts of the MAMP stack
• Understand PHP data types and basic syntax

What is PHP?

PHP is a common back-end language. In fact, it is estimated that of all websites with an identifiable back-end, PHP is the language for over 83% of them. Yes. That is a real number. And fun fact: it was 82% last time we checked.

Why is it so common? Well, there's something to be said for trend-setters like Facebook using a PHP-derived backend to build their product out, and providing SDKs (Software Development Kits) for PHP. But, more importantly, PHP is used in most of the popular CMSes (Content Management Systems). Specifically, Wordpress is based on PHP, and just under 30% of the Internet's websites are on Wordpress. And 100% of those are built with PHP on the back-end.

A Little History

PHP is actually arguably older than Javascript (it was developed first, but released slightly later). It has been around since the mid 90s as a way to dynamically render HTML for a web browser, based on variables and the functionality available to a full programming language.

It was developed as a toolset to make building a Personal Home Page easier. After its popularization, the creator claimed that PHP stood for PHP: Hypertext Preprocessor, which is a wonderfully complicated name. Finally its name stopped meaning anything, just like npm or Häagen-Dazs.

The latest production version of PHP is 7. What happened to PHP 6? Long story short, they made a couple big mistakes, and decided skip right over to version 7 - same as Angular did with v3 or ES with v4.

Remember: Pour one out for our lost versions

Oh, and PHP has the best mascot ever: the elephpant:

What is MAMP?

MAMP is another stack, like MEAN. It is a combination of the:

• Mac Operating System
• Apache Web Server
• MySQL dialect of SQL
• PHP back-end language

You might also hear of WAMP (AMP on Windows) and LAMP (AMP on Linux)

Setup

Follow the directions below to set up the MAMP stack on your computer.

1. Open MAMP
2. Click Start Servers
3. Go to http://localhost:8888/
4. You should have a directory called mamp inside your WDI working directory--make a new directory inside your mamp directory called php-practice
5. Put a file inside this directory called index.php
   • This is where we will be working in this lesson

Note: If you are troubleshooting back-end issues, MAMP error logs are in /Applications/MAMP/logs/ - tail -f php_error.log to see errors

Basics

Tags

Because this is all run on top of Apache, the initial assumption is that we're serving static HTML files

• We need <?php ?> tags to show that we're writing PHP
• Think of this as if Apache/PHP is our server.js and we're just writing EJS

Instead of <%= %> you have <?= ?> or <?php echo ?>

Instead of <% %> you have <?php ?>

Comments

// single line comment

/*
multi
line
comment
*/

Declaring/Assigning variables

Use a $ before a variable name to tell php it is a variable. Assignment is standard.

<?php
	$my_first_var; //declare
	$my_first_var = 2; //assignment
	$my_second_var = 3; //declare and assign
?>

Data Types

<?php
$x = "my string";
var_dump($x);
?>

<?php
$x = 5985;
var_dump($x);
?>

<?php
$x = 10.365;
var_dump($x);
?>

<?php
$x = true;
var_dump($x);
?>

<?php
$cars = array("Volvo","BMW","Toyota");
var_dump($cars);
?>

<?php
$x = null;
var_dump($x);
?>

String Operators

Use a . or .= to combine strings.

<?php
	$first_part = "first part";
	$second_part = "second part";
	$concatenation = $first_part . " " . $second_part; //combine strings
	$concatenation .= ".  Appended value"; //append strings
	echo $concatenation;
?>

Now try it yourself!

Arithmetic Operators

<?php
	1 + 1; //2
	2 - 1; //1
	3 * 2; //6
	12 / 3; //4
	5 % 2; //1 modulus
	2 ** 3 //8 exponents
?>

Increment/Decrement Operators

<?php
	$x++; //increment by 1;
	$x--; //decrement by 1;
?>

Assignment Operators

<?php
	$my_var = 1;
	$my_var += 1; //$my_var = $my_var + 1;
	$my_var -= 1; //$my_var = $my_var - 1;
	$my_var *= 2; //$my_var = $my_var * 2;
	$my_var /= 2; //$my_var = $my_var / 2;
?>

Now try it yourself.

• Create five numerical variables, using all of the mathematical operators above.
• Increment one of them.
• Multiply one of them by two using an assignment operator.
• Echo all five variables out.

Conditionals

Formats

Format 1:

<?php
	if(condition){
	}
	elseif(condition2){
	}
	else{
	}
?>

Format 2:

<?php if(condition): ?>
<?php elseif(condition2): ?>
<?php else: ?>
<?php endif; ?>

Comparison Operators

<?php
	$x == $y; //equal
	$x === $y; //identical
	$x != $y; //not equal
	$x !== $y; //not identical
?>

Arithmetic:

<?php
	$x < $y; //less than
	$x > $y; //greater than
	$x <= $y; //less than or equal to
	$x >= $y; //greater than or equal to
?>

Logical Operators

<?php
	true && false //AND operator
	true || false //OR operator
?>

Independent Practice

Use "Format 2" above to display one of three <h1> tags, depending on whether a number is greater than zero, less than zero, or equal to zero.

Arrays

Indexed Arrays

Standard array functionality

<?php
$cars = array("Volvo", "BMW", "Toyota");
$cars[4] = 'Volkswagen'; //can be in indexes that don't yet exist
$cars[] = "AND JET PLANES"; //pushes onto array
echo "I like " . $cars[0] . ", " . $cars[4] . " " . $cars[5] . ".";
echo "<br><br>"; // adds a double line break
echo count($cars);//prints length of array
echo "<br><br>"; // adds a double line break
print_r($cars); //prints contents of array in nicer format than var_dump
?>

Associative Arrays (hashes)

These are very similar to Javascript objects

<?php
	$age = array("Peter" => 35, "Ben" => 37, "Joe" => "43"); //declare
	$age = array("Bob"=> 105); //add at a new position
	echo "Bob is " . $age['Bob'] . " years old.";
?>

Loops

While

<?php
$x = 1;

while($x <= 5) {
    echo "The number is: $x <br>";
    $x++;
}
?>

<?php $x = 1;?>
<?php while($x <= 5): ?>
	<li><?= $x ?></li>
	<?php $x++ ?>
<?php endwhile; ?>

For

<?php
for ($x = 0; $x <= 10; $x++) {
    echo "The number is: $x <br>";
}
?>

<?php for ($x = 0; $x <= 10; $x++): ?>
    <li>The number is: <?= $x ?></li>
<?php endfor; ?>

Foreach

<?php
$colors = array("red", "green", "blue", "yellow");

foreach ($colors as $key => $value) {
    echo $key . ": $value <br>";
}
?>

<?php $colors = array("red", "green", "blue", "yellow"); ?>
<?php foreach ($colors as $key => $value): ?>
	<?= $key ?>: <?=$value?> <br>
<?php endforeach; ?>

This works for associative arrays too:

<?php
$ages = array("Peter" => 35, "Ben" => 37, "Joe" => "43");

foreach ($ages as $key => $value) {
    echo $key . ": $value <br>";
}
?>

<?php $ages = array("Peter" => 35, "Ben" => 37, "Joe" => "43"); ?>
<?php foreach ($ages as $key => $value): ?>
	<?= $key ?>: <?=$value?> <br>
<?php endforeach ?>

Functions

<?php
function writeMsg() {
    echo "Hello world!";
}

writeMsg(); // call the function
?>

Convenience Methods

Strings

Count a string's length

<?php
echo strlen("Hello world!"); // outputs 12
?>

Count number of words in a string

<?php
echo str_word_count("Hello world!"); // outputs 2
?>

Reverse a string

<?php
echo strrev("Hello world!"); // outputs !dlrow olleH
?>

Find a sub string in a string

<?php
echo strpos("Hello world world!", "world"); // outputs 6
//search from the right
echo strrpos("Hello world world!", "world"); // outputs 12
?>

Replace text within a string

<?php
echo str_replace("world", "Dolly", "Hello world!"); // outputs Hello Dolly!
?>

Get a substring based on character index

<?php
//second param is index (0 based, like an array)
echo substr("Hello world", 3); // outputs 'lo world'
//third param is length of string
echo substr("Hello world", 3, 4); // outputs 'lo w'
?>

Want more? Here is a full reference for all PHP string methods.

Sorting Arrays

Various functions for sorting arrays. Can be done arithmetically or alphabetically, depending on content

• sort() - sort arrays in ascending order
• rsort() - sort arrays in descending order
• asort() - sort associative arrays in ascending order, according to the value
• ksort() - sort associative arrays in ascending order, according to the key
• arsort() - sort associative arrays in descending order, according to the value
• krsort() - sort associative arrays in descending order, according to the key

These functions affect the actual array they are called on.

$cars = array("Volvo", "BMW", "Toyota");
sort($cars);
print_r($cars); //BMW, Toyota, Volvo

Classes and Objects

Public Members

<?php
class Car {
	public $wheels = 4; // public var can be modified outside class definition
}

$my_car = new Car();

print_r($my_car);
$my_car->wheels = 3;
print_r($my_car);
?>

Protected Members

<?php
class Car {
	protected $wheels = 4; // cannot be accessed outside class definition
	//must define getters...
	public function getWheels(){
		return $this->wheels;
	}
	//and setters...
	public function setWheels($new_wheel_value){
		$this->wheels = $new_wheel_value;
	}
}

$my_car = new Car();
echo $my_car->getWheels();
$my_car->setWheels(5);
echo $my_car->getWheels();
echo $my_car->wheels; //error: cannot access protected property
?>

Constructors

<?php
class Car {
	public $wheels;
	public function __construct(){ // runs at beginning of object creation
		$this->wheels = 4;
	}
}
?>

Inheritance

<?php
class Car {
	protected $wheels = 4; //accessible by child class, not outside class, though
	private $engine_on = false; //unaccessible by child class
	public function getWheels(){
		return $this->wheels;
	}
	public function setWheels($new_wheel_value){
		$this->wheels = $new_wheel_value;
	}
	public function start(){
		$this->engine_on = true;
	}
}

class Humvee extends Car {
	protected $armour = 10;
	public function takeDamage($damage){
		$this->armour -= $damage;
	}
	public function loseWheel(){
		$this->wheels--; //can access parent $wheels member
	}
	//can extend parent's start function
	public function start(){
		parent::start(); //run parent's start function
		//parent::$engine_on = false; //errors out: cannot access private member of parent
		echo "WELCOME TO THE JUNGLE...";//then do something else
	}
}

$my_humvee = new Humvee();
print_r($my_humvee);
$my_humvee->loseWheel();
print_r($my_humvee);
$my_humvee->takeDamage(6);
print_r($my_humvee);
$my_humvee->start();
print_r($my_humvee);
?>