Client - Server

The Client (The browser):

request a Web page

retrieve (all of) it

render it

The Server:

Stores html, media, image etc. files

Connected to the WWW

Waits for requests from browsers

Locates and sends a resource on request

📷 View Client/Server Example

Web Server

Responds to client requests by providing resources

URL (Uniform Resource Locator)

Can access Database Management System (DBMS)

e,g MySQL - a popular choice of database for use in web applications,

Server-side scripts

Executed on server

Generate custom response for clients

Wide range of programmatic capabilities

Access to server-side software that extends server functionality

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X

Client-side scripts

Validate user input

Reduce requests needed to be passed to server

Access browser

Enhance Web pages with HTML (HTML5) / CSS / Javascript
PHP

PHP: Hypertext Preprocessor

Server-side scripting language

Open source

Free

Script runs on server to produce html

.php files

🔗 www.php.net

A PHP script is executed on the server

The plain HTML result is sent back to the browser.

A PHP script can be placed anywhere in the document.

PHP code is executed on the server

generating HTML which is then sent to the client.

The client would receive the results of running that script, but would not know what the underlying code was.

What Can PHP Do?

PHP can generate dynamic page content

PHP can create, open, read, write, delete, and close files on the server

PHP can collect Form data

PHP can add, delete, modify data in your database

PHP can be used to control user-access

PHP can encrypt data
Introduction:

Hello World - 💡 HelloWorld.php

echo used to output text onto a web page:
```
<html>
  <body>
   <h1> PHP Example (This is HTML ) </h1>
   
    <?php
     echo "Hello World (This is PHP)  ";
    ?>
  </body>
</html>
```
To execute the PHP code:

A php file MUST be run on a Web Server

e.g Xampp

Note the Server Address – for example :

localhost/...... /HelloWorld.php

Server Address (URL)

If it is run on the Client only :

PHP code will NOT be executed

Will ONLY view HTML

PHP

PHP is a scripting language ( as is Javascript)

PHP is Loosely typed language (similar to Javascript)

Variable automatically converted to correct data type when to fit assigned value

Variables and Types

Variables start with a $ symbol followed by a letter or underscore and other alpha_numeric characters – no spaces
```
$color = “purple”;
```
PHP IS Case –Sensitive for Variable Names :
```
<?php
  $color = "red";
  echo "My car is " . $color . "<br>";
  echo "My house is " . $COLOR . "<br>";
  echo "My boat is " . $coLOR . "<br>";
?>
```
$COLOR and $coLOR are DIFFERENT variables – they have NOT been declared – so will NOT be displayed

Operators

Arithmetic

+   -   *   /   %   ++   --

Assignment

=   +=   -=   *=   /=   %=   .=

Comparison

==   !=   <>   >   <   >=   <=

Logical

&&   ||   !

PHP String Operations – 💡 strings.php

. - concatenate …a full-stop !!

All of these will output : My name is Brian Shields

<?php    
 echo "My name is " . " Brian Shields ";
  // join two text strings

 $fname = "Brian";
 echo "My name is " . $fname . " Shields";
 // join two text strings and  variable (text string)
  
 $sname = "Shields"; 
 echo "My name is " . $fname . " " .  $sname;  
// join a text string and  two variables (text strings ) - also need to add a space character

$fullname = $fname . " " .  $sname;   
// create a  variable (text string) from two other text strings
 echo "My name is " . $fullname;

 
 $fulltext = "My name is " . $fname . " " .  $sname;  
// create a  variable (text string) which contains all text - including variables
 echo $fulltext;
?>

Other Functions

💡 Strings_Other_Functions.php

str_word_count 
//counts the number of words in a string

strtoupper  
//convert string to UPPER CASE

str_shuffle 
//shuffles a string

str_replace  
//Replace all occurrences of the search string with the replacement string

Other Functions cont...

<?php

  $fname = "Fred";
  $sname = "Smith";
  
  $str = $fname . " " . $sname;
  echo "The string is : " . $str;
  echo "<br/>";
  
  $num_words = str_word_count($str);
  echo "Word Count of the string is : " . "$num_words";
  echo "<br/>";
  
  $upper_word = strtoupper("$name");
  echo "Surname upper case is: " . "$upper_word";
  echo "<br/>";
  
  $shuffled_name = str_shuffle("$sname");
  echo "The shuffled surname is : " . $shuffled_name;
  echo $str2;
  echo "<br/>";
  
  $str_new = str_replace("Fred", "Mary", $str);
  echo "Fred has been replaced by Mary and the new string is :" . $str_new;
  echo "<br/>";  
?>

Selection

if (condition)
  code to be executed if condition is true;

if ... else

if (condition)
   code to be executed if condition is true;
else
   code to be executed if condition is false;

if ... elseif ... else

if (condition)
    code to be executed if condition is true;
elseif (condition)
    code to be executed if condition is true;
else
    code to be executed if condition is false;

Switch

switch (n)
{
case label1:
  code to be executed if n=label1;
  break;
case label2:
  code to be executed if n=label2;
  break;
default:
  code to be executed if n is different from both label1 and label2;
}

Iteration

while

while (condition)
{
   code to be executed;
}

do ... while

do
{
  code to be executed;
}
while (condition);

for

for (init; condition; increment)
{
  code to be executed;
}

foreach

foreach ($array as $value)
{
   code to be executed;
}

Arrays

Numeric

$cars=array("Saab","Volvo","BMW","Toyota");
$cars[0]="Saab";
$cars[1]="Volvo";

Associative - each ID key is associated with a value

$ages = array("Peter"=>32, "Quagmire"=>30, "Joe"=>34);
$ages['Peter'] = "32";
$ages['Quagmire'] = "30";

Functions

script automatically executes when a page is loaded except if it is in a function

function functionName()
{
  code to be executed;
}

function can be called from anywhere in page

<?php
   function writeFullName()
   {
      echo “Brian Shields";
   }
   echo "My name is ";
   writeFullName();
?>

Output: My name is Brian Shields

Parameters

<?php
  function writeNames($fname)
  {
     echo $fname . " Smith.<br />";
  }
  echo "My name is ";
  writeNames(“Fred");
  echo "My sister's name is ";
  writeNames(“Jean");
  echo "My brother's name is ";
  writeNames(“John");
?>

Output:
My name is Fred Smith
My sister's name is Jean Smith
My brother's name is John Smith

Return Value

<?php
  function add($x,$y)
  {
      $total=$x+$y;
      return $total;
  }
  //Note the use of String Concatenation
  echo "1 + 16 = " .  add(1,16);
?>

Output: 1 + 16 = 17

💡 Functions.php

Video

📹 Watch Functions

Client - Server

Web Server

PHP

Introduction:

PHP

Variables and Types

Operators