notes PHP

👈Prev 🏡Primary Notes Next👉

Introduction

PHP is a server side scripting language

Stands for PHP hypertext programing (go and figure what that stands for)

Released in 1995

Has some issues:

30% of vulnerabilities are related to PHP
Sloppy code leads to errors.

PHP is run on the server side can collect data from:

databases
web services
files
email
other software

Basic

the file name needs to be changes from .html to .php

all php code must be written inside <?php and ?>

all php statements end with a semicolon

comments are:

//single line
/* multi-line */

Simple Commands

echo inserts the output into the larger html page including any tags

echo <p><strong> Hello </strong></p>

print f

print f produces formatted statements form variables

printf("String",variables)

$product= box;
$weight = 1.756723;
printf("the %s is %.2f kilos",$product,$weight);

Specifier	Type
%f	float
%s	string
%d	decimal

NUll Coalescing Operator

?? can be used to assign a value if a variable is null $username= $GET_["username"]??default

more here

Variables

Variable prefixed with $
must start with letter or _
only contain alphanumerical characters and _
No spaces
case sensitive
Dynamically typed

$a = 3;
$b = 4;
echo $a+$b;

constants

Use define()

define("PI",3.141592653);
$pi=PI;

Data Types

Scalar types

integer
float / double (these are the same)
boolean
string

Compound Types

Array
Object

Strings

need double quotes

concatenation uses . can use .= for append

$a = "Hello"
$b = "World"

$c = $a." ".$b
$a .= " "
$a .= $a

--
$a -> Hello World
$c -> Hello World

Arrays

Two types

Numeric Array
Associative array

Numeric Array

Creation: $courses=("CS139","CS132","CS133");

You can also do:

$courses[0]="CS139";
$courses[1]="CS132";
$courses[2]="CS133";

Associative Array

Creation:

$courses=("CS139"=>"Web Dev","CS132"=>"Not A Cult","CS133"=>"Professional Skills");

You can also do Representation:

Operators

Arithmetic Operators

Operator	Name
`+`	Addition
`-`	Subtraction
`*`	Multiplication
`/`	Division
`%`	Modulus
`++`	Pre/Post increment
`--`	Pre/Post decrement

Comparison Operators

Identical same value and same type 5 is not identical to “5”

Logical Operators

Operator	Name
`&&`	AND
`\|\|`	OR
`!`	NOT

Array Operators

Operator	Name
`$arr1 +$arr2`	Union
`$arr1 == $arr2`	Equal
`$arr1 === $arr2`	Identical

Branching

If

similar to Java

if ($course == "CS139") {
    echo "Web Dev";
} elseif ($course =="CS132"){
    echo "not a cult";
} else{
    echo "Not Web Dev and not not a cult";
}

can use : instead of {}

Switch

switch($course){
    case "CS139":
        echo "Web Dev";
    break;
    case "CS132":
        echo "not a cult";
    break;
    default:
        echo "Not Web Dev and not not a cult";
}

only judges by equality by if they are identical.

Looping

For loop

for ($x=0; $x <=10; $x++){
    echo "$x <br>";
}

While Loop

$x=0;
while ($x<=10){
    echo "$x <br>";
    $x++;
}

do while loop

$i=0;
do {
    echo "$x <br>";
    $x++;
} while ($x<=10);

Array Iteration

iterate over an array obtaining the value at each location

foreach($array as $item){
    echo $item;
}

for associative arrays

foreach($array as $key => $value){
    echo $key."is".value;
}

Function

Functions that have a return value can also (optionally) have a a return type

function FunctionName ($arg1,$arg2):string{
    return $arg1.$arg2;
}

Pass by Reference

Adding an & in front passes by reference, a variable change in a function is reflected outside the function scope

function add(&$arg){
    $arg+=100;
}

Global

Global scoped variables can be included in functions with global

SHOULD BE AVOIDED

$a ="a";
$b ="b";
function findAB(){
    global $a,$b
    echo $a.$b
}

HTML Forms

In PHP the data is converted from the requests to associative arrays. Post requests are $_POST get requests are $_GET

PHP From Another File

Php can insert the contents of another file

require <script.php>, script stops if file can’t be found

include <script.php>, script attempts to continue if file cant be found

also

include_once , require_once

Elements such as header or nav bar only need to be made once then can be copied over

Objects and Classes

class Person{
    var $name;
    function get_name(){
        return $this->name;
    }
    function set_name($new _name){
        $this->name=$new_name;
    }
}

All object variables need to be specified through $this->

Call Methods

To call a method $object->method(<args>)

Constructor

The constructor function is always __construct()

Objects can be created through the new keyword

$James= new Person();

Access Modifier

public
private
protected

can all be used to define access these should replace the var keyword or put in front of a function

Inheritance

class Admin extends User

parent class method id called by

parent::method();

Cookies

Cookies can be added with the setcookie() function

$expiry = time()+60*60*24*7;
$name="Username";
$value="James";
setcookie($name,$value,$expiry);

cookies can be fetched using $_COOKIE[value]

if (isset($_COOKIE["Username"])){
    echo $_COOKIE["Username"];
}

Sessions

To create a session use session_start() this must occur at the start of the file

can be used with $_SESSION[]

set with $_SESSION['Key'] = $value;

and retrieve with $value =$_SESSION['Key'];

values can be checked with isset($_SESSION['Key'])

session_destroy() can be used for logging out and removing all values

example to check if a user is logged in

<?php
session_start();
if (isset($_SESSION['UserID'])){
    // show page content here
}
else{
    header(`location:HomePage.php`);
}
?>

Password Hashing

Passwords should be hashed for storing to ensure security the hashes can be created with password_hash() and verified with password_verify($password,$hashedPassword)

if (isset($_POST['username']) && isset($_POST['password'])){
    $password = $_POST['password'];
    $hashedPassword = getHashedPassword($_POST['username']);
    if (password_verify($password ,$hashedPassword)){
        header(`location:restrictedPage.php`);
    }else{
        header(`location:HomePage.php`);
    }
}else{
    header(`location:HomePage.php`);
}

It is important to verify that a user is logged in before they can access a page

<?php
require `access.php`;
require_login();
?>

can be put at the top of pages to check if the user is logged in.

inside access.php:

<?php
function require_login(){
    if (!isset($_SESSION['id'])){
        header("Location:index.php");
        exit();
    }
}
?>

if $_SESSION['id'] is set when the user logs in this will prevent users from accessing pages unless they have logged in

SQL

first a database connection must be established

$db = new SQLite3('database.db');

the database can then be queried

$db->exec(<SQL>) for result less queries

$db->query(<SQL>) which returns a result

handing a query result

$result = $db->query("SELECT * FROM Users");

while ($row = $result->fetchArray()){
    echo $row['username'];
}

Serialization

can be used for storing objects and complex data as a string $string = serialize($object);

the text can then be un-serialized $object= unserialize($string);

Reading and Writing Files

two types oif access stream access, will read a small portion at a time. All-in-Memory access can read the entire file to memory.

Stream Access

similar to ‘C’

fopen() - opens the file
fgets() - gets a portion of the file
fclose()- closes the file

In-memory Access

file() Reads the entire file and returns an array of each line in the file
file_get_contents() Read the entire file and return a string
file_put_contents() Writes the contents of a string variable to a file

Errors

3 types of errors

Expected Errors - typing in the wrong name
Warnings - thing to warn the user about, start before end dates
Fatal Errors - things that stop the process, should still be recoverable

Reporting

error reporting can be done with

error_reporting(E_ALL);
ini_set("display_errors",1);

Superglobals

Name | Description –|– $Globals | Array For storing data that needs the superglobal scope $_Cookies | Array of cookie data passed via HTTP request $_ENV | Array of server environment data $_FILES | Array of files uploaded to the server $_GET | Array fo query string data passed to the server via the URL $_POST | Array fo query string data passed to the server via the HTTP header $_REQUEST | Array containing the contents of $_GET, $_POST, $_COOKIES $_SESSION | Array containing session data $_SERVER | Array containing information about the request and the server

$_SERVER["HTTP_REFERRER"] information about where the user came from

$_FILES used with post requests HTTP should have a file input type for a form

$_FILES["File1"]["name"] - anme fo the file
$_FILES["File1"]["type"] - e.g img.png
$_FILES["File1"]["tmp_name"] where is was upladed to
$_FILES["File1"]["error"] “UPLOAD_ERR_OK” if no error
$_FILES["File1"]["size"] in bytes

then move_uploaded_file($tmp_file,$new_file);

Table of Contents