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• The first word of the acronym is an acronym, recursive backronym, originally the acronym stood for Personal Home Page
• Developed in 1994
• PHP is a server scripting language. It can send emails, process a contact form, or connect to a database. HTML, CSS, JS are run on web browser, and we can not use them to store the user info permanently, because the browser gets closed down and we want a way to store that data somewhere centrally so that user can access it anywhere on the web.

(HTML...CSS...JS...WebGL)Web Browser <---->internet<----->Web Server (PHP...MySQL, Apache, Server Modules)

So languages that work on the web server allow us to do the web service-specific things like logging a user in or returning their tweets or saving their progress in a game.

• PHP is powering 81.8% of the web as of 2021.
• It's a language in which WP is built and learning PHP will enable you to create WP plug ins, customize WP themes and etc.
• .php file can contain HTML, CSS, JS and PHP code.

• create a separate new file, call it php.ini, it will contain initialization options

• set 2 variables

• error_reporting = E_ALL

• meaning report on any type of errors and

• display_errors = On

• these will allow displaying errors when we develop site. If it's online, need to delete them so the hackers won't use the error messages to access your website.

• if error message refers to line 6, the error may be on previous line, because the error was not detected until line 6.

• echo "Hello World"; --> displays text in php. Use only semi columns.

• must put HTML outside of these tags

<?php some php code here?>

<?php$name ="Rob";?>

example:

<?php$name ="Rob";echo"My name is$name";?>

It will display variable value -->

my name is Rob

<?php$name ="Rob";echo$name;?>

it will display -->

Rob

• How to put strings together (Concatenating)

$string1 ="This is the 1st part of a sentence";$string2 ="here you have the 2nd one";echo$string1.$string2;

." ". is used to put a space between strings

you can put HTML inside those strings to make them appear on different lines. Add<p> tag.

$string1 ="<p>This is the 1st part of a sentence</p>";$string2 ="<p>here you have the 2nd one</p>";echo$string1."".$string2;

• PHP Variables containing a string of numbers

$myNumber =45;$calculation =$myNumber *31 /97 +4;echo$calculation;

it will display -->

18.381443298969

for multiplication use asterisk (*)

$myNumber =45;$calculation =$myNumber *31 /97 +4;echo"The result of the calculation is".$calculation;

• Boolean variables in PHP

$myBool =true;echo"<p>This statement is true?".$myBool."</p>";

It will show -->

1

$myBool =false;echo"<p>This statement is true?".$myBool."</p>";

It will show -->

0 or nothing

Note: it doesn't give true false, but 1 or 0. This is how PHP treats true and false.

• Store Variable names within variables:

$name ="Mari";$variableName ="name";echo$$variableName;

$myArray =array("a","b","c","d");print_r($myArray);shows -->

Array ( [0] => a [1] => b [2] => c [3] => d )

print_r shows the contents of the array (_r stands for readable)

In the page source, it displays like -->

Array(    [0] => a    [1] => b    [2] => c    [3] => d)

• Get items from Array

echo$myArray[1];

displaysb

• Define an array by creating values manually:

the arrays are associative, meaning you can put anything you like in the index, e.g. jump from 2 to 5 or call it "myFavouriteFood"

$anotherArray[0] ="a";$anotherArray[2] ="b";$anotherArray["myFavouriteFood"] ="ice cream";print_r($anotherArray);

• Putting line breaks:

echo"<br><br>";

• If you want to make an associative PHP array like "myFavouriteFood" to store info about password, username, etc, then:

$thirdArray =array("France" =>"French","USA" =>"English");print_r($thirdArray);

Shows -->Array ( [France] => French [USA] => English )

• Get the length of the array (number of items in the array)

echosizeof($thirdArray);

Shows -->2

• Add an item to the end of an array

$myArray =array("a","b","c","d");$myArray[] ="e";print_r($myArray);

• Remove item using unset command

$myArray =array("a","b","c","d");unset($myArray["0"]);print_r($myArray);

Shows -->

Array (    [1] => b    [2] => c    [3] => d )

$user ="rob";if ($user =="rob") {echo"Hi Rob!";}else {echo"I don't know you";}

$age =25;if ($age >=18 ||$user =="rob" ) {echo"you may proceed..";}else {echo"You're too young, sorry!";}

Note: || means OR

When Gmail is showing all of your emails that's a loop because it's looping all the emails and displays them for you.

for loopvar counter variablei counter variable namei = 0 settingi to its initial value

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

it will display0 1 2 3 4 5 6 7 8 9

for ($i =2;$i <=30;$i =$i +2) {echo#i."<br>";}

it will display2 4 6 8 10 12 14up to30 including.

for ($i =10;$i >=0;$i--) {echo#i."<br>";}

It will display10 9 8 7 6 5 4 3 2 1 0

$family =array("rob","Tommy","M");for ($i =0;$i <sizeof($family);$i++) {echo$family[$i]."<br>";}

It will display -->rob Tommy M2nd method isforeach loop

foreach ($familyas$key =>$value) {echo"Array item".$key." is".$value."<br>";}

it will display -->

Array item o is Rob

Array item 1 is Tommy

Array item 2 is M

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

It shows0 1 2 3 4 5 6 7 8 9 10

$i =5;while ($i <=25) {echo$i."<br>";$i =$i +5;}

if you use instead of $i++ e.g.

$i = $i +5;

it will increase numbers by 5 and show5 10 15 20 25or another way:

$i =1;while ($i <=10) {$j =$i *5    echo$j."<br>";$i++;}

To present items from the array: 

$family =array ("A","B");$i =0;while ($i <sizeof($family)) {echo$family[$i]."<br>";$i++;}

It shows items:A B

1. Get variable in the URL string -->/?name=rob&password=1234&gender=male

to access them need to know that they are contained in the $_get. So you need to type

print_r($_GET);

to present a particular value:

echo$_GET("gender")

2. Use a form:

As HTML:

<p>What is you name?</p><form><inputname="name"type="text"><inputtype="submit"value="Go!"></form>

For PHP:

echo"Hi there"$_GET['name']."!"

and you get Hi there and any name you input in the form's input field.

• Challenge:Filename:is_it_prime.php

<p>What is you name?</p><formmethod="post"><inputname="name"type="text"><inputtype="submit"value="Go!"></form>

for PHP -->

print_r($_POST);

If you will want to submit some data twice, you'll get a pop-up telling you to confirm the resumbition.

• Challenge: When a user enters their name program checks to see if the name is on the array of usernames. If so, hello ...name... is shown on the page.Filename:checking_users.php