# PHP

Example class

namespace namespaceName;

//Example include other file
require_once("ParentClassName.php");

/**
* Example of class (with Parent class)
*/
    class ClassName extends ParentClassName {
	    private $privateMemberVariable;
	    public $publicMemberVariable;

/**
* Example of constructor with argument
*/
	public function __construct(string $constructorStringArgument) {
		$this->privateMemberVariable = "dont forget $this-> on member variables ";
	}


/**
* Example of returning a member variable
*/
public function getMember() : string { //note the type-safe return value of type string
		return $this->privateMemberVariable;
	}


	/**
	* Example string concatination
	*/
	public function getMemberPlusOther(string $other) : string { 
		return $this->privateMemberVariable . $other;  //Note the "." operator
	}
}

An object is used using the "new" keyword


$e = new Exception();

Note that parameters might need to be sent


$e = new Exception("Something bad happened");

Get and set


<?php
	class Adress {

	}

	class Person {
		private $adress;

		/* Method parameter with type-hinting */
		public function setAdress(Adress $typedArgument) {
			$this->adress = $typedArgument;
		}

		/* Method to access a private member variable*/
		public function getAdress() {
			return $this->adress;
		}
	}
	

//if-statements
if ($i < $sum) {
	$sum = $i;
} else if ($i > $sum) {
	$sum = $i;
} else {
	
}

//for-loop with variable
$arr = array(1,2,3);
for ($i = 0; $i < count($arr); $i++) {
	echo "index $i value " . $arr[$i] . " ";
}

//foreach-loop
foreach ($arr as $key => $value) {
	echo "index: $key value: $value ";
}

//while loop
while (true) {
	echo "this will result in a memory overflow..."; 
}


//exception 
try {
	throw new \Exception("an exeption occured");
} catch(\Exception $e) {
	echo "An exception was captured";
} 

Good to know PHP Api-methods


//Check if a variable is a atring
if (is_string($name) === false) { 
}

//count the number of values in an array
$someArray = array();
if (count($someArray) == 0) {
}

//check if an unknown variable is a number
if (is_numeric($element)) {
    echo "'{$element}' is numeric", PHP_EOL;
} else {
    echo "'{$element}' is NOT numeric", PHP_EOL;
}

//Check if a number is finite
if (is_finite($largeNumber)) {
	echo "the number is finite";
}

//Check if a number is infinite
if (is_infinite($largeNumber)) {
	echo "the number is infinite";
}

Global scope variables
A global scope variable can be declared directly in the PHP file.


<?php
	$globalVariable = 4;
	

Function parameters and Local variables
Function parameters does not have to have a type even if I recommend that you do. A variable that is locally declared in the scope of the method can only be used inside the method.


<?php

	function exampleFunction($parameter) {
		$localVariable = $parameter;
	}
	

Class member variables

The following PHP application creates a public member variable named "name"

Variable-declarations in PHP does not use a type-hint except for classes and arrays as arguments to methods or functions.


<?php
	//Declaration
	class Person {
		public $name = "Daniel";
		protected $age = 35;
		private $phoneNumber = "555-12345";
	}

	//Usage 
	$student = new Person(); //create an object
	$student->name = "Linda";

	echo $student->phoneNumber; //not allowed due to the private scope
	

Visibility
The three keywords private, protected and public decides how the variable or method can be used from other classes.

    private - can only be used within the class
    protected - can only be used within the class and by classes that inherit from the class
    public - can be used by anyone

Import files
To access a class in another file use the "require_once" method.


<?php
	
require_once("Person.php");

$p = new Person("Daniel");

Example, store a value in a member variable

Note that for class-member variables and functions you always need to access them through "$this->"


<?php
	class Adress {

	}

	class Person {
		private $adress;

		/* Method parameter with type-hinting */
		public function setAdress(Adress $typedArgument) {
			$this->adress = $typedArgument;
		}

		/* Method to access a private member variable*/
		public function getAdress() {
			return $this->adress;
		}
	}
	

Dependency Injection

A value supplied in a class constructor is either used to compute the inner state of the object (used inside the constructor itself) or it is stored in a member variable for use in member methods.


<?php
	class Adress {

	}

	class Person {
		private $adress;

		public function __construct(Adress $typedArgument) {
			$this->adress = $typedArgument;
		}

		/* Method to access a private member variable*/
		public function getAdress() : Adress{
			return $this->adress;
		}
	}