php-notes/PHP.md

PHP

Setup

1. Download [MAMP] (https://www.mamp.info/en/downloads/)
2. Double click .pkg file and follow prompts
3. Double click /Applications/MAMP/MAMP
4. Point MAMP to working directory
   • Click on Preferences
   • Click on Web Server
   • Click the folder icon next to "Document Root" and find a suitable directory to work out of
   • Click OK
5. Go to http://localhost:8888/
6. Error logs are in /Applications/MAMP/logs/
   • tail -f php_error.log
7. MAMP stands for Mac, Apache, MySQL, PHP
   • this describes the tech stack
     • Mac
       • Your OS
     • Apache
       • A pre-build web server that serves static files
       • Is extendable with various modules that allows it to do many things easily
     • MySQL
       • Your Database
     • PHP
       • A module for Apache that allows it to server dynamic data

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 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;
?>

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;
?>

Conditionals

Formats

Format 1:

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

Format 2:

<?php if(condition): ?>
	condition1
<?php elseif(condition2): ?>
	condition2
<?php else: ?>
	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
?>

Arrays

Indexed Arrays

Standard array functionality

<?php
$cars = array("Volvo", "BMW", "Toyota");
$cars[4] = 'asdf'; //can be in indexes that don't yet exist
$cars[] = "added to end"; //pushes onto array
echo "I like " . $cars[0] . ", " . $cars[4] . " and " . $cars[5] . ".";
echo count($cars); //prints length of array
print_r($cars); //prints contents of array in nicer format than var_dump
?>

Associative Arrays (hashes)

These are very similar to Ruby hashes

<?php
	$age = array("Peter" => 35, "Ben" => 37, "Joe" => "43"); //declare
	$age["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:

<?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'
?>

Turn a string into an array based on some delimeter

<?php
    $the_string = "Some sentence goes here";
    $string_array = explode(" ", $the_string);
    var_dump($string_array);
?>

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 accessed outside class definition
}

$my_car = new Car();

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

Constructors

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

Protected Members

<?php
class Car {
	protected $wheels; // cannot be accessed outside class definition
	//must define getters...
	public function getWheels(){
		return $this->wheels;
	}
	public function __construct($num_wheels){ // runs at beginning of object creation
		$this->wheels = $num_wheels;
	}
}

$my_car = new Car(4);
echo $my_car->getWheels();
echo $my_car->wheels; //error: cannot access protected property
?>

Statics

<?php
class Car {
	protected $wheels; // cannot be accessed outside class definition
	//must define getters...
	public function getWheels(){
		return $this->wheels;
	}
	public function __construct($num_wheels){ // runs at beginning of object creation
		$this->wheels = $num_wheels;
	}
}
class CarFactory{
	static protected $cars = array();
	static public function create($num_wheels){
		$new_car = new Car($num_wheels);
		self::$cars[] = $new_car;
		return $new_car;
	}
	static public function find($index){
		return self::$cars[$index];
	}
}
$my_car = CarFactory::create(2);
$my_car2 = CarFactory::create(4);
print_r($my_car);
print_r(CarFactory::find(1));
print_r(CarFactory::$cars); //errors out: protected
?>

Inheritance

<?php
class Car {
	protected $wheels; //accessible by child class, not outside class, though
	private $engine_on = false; //unaccessible by child class
	public function __construct($num_wheels){ // runs at beginning of object creation
		$this->wheels = $num_wheels;
	}
	public function getWheels(){
		return $this->wheels;
	}
	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
	}
}

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