PHP and MYSQL - … · > PHP supports many databases (MySQL, Informix, Oracle, Sybase, Solid, ... > Variables are used for storing values, like text strings, numbers or arrays.

PHP and MYSQL

PHP Introduction

PHP is a recursive acronym for “PHP: Hypertext Preprocessor” -- It is a widely-used open source general-purpose serverside scripting language that is especially suited for web development and can be embedded into HTML.

PHP Introduction

> PHP is a server-side scripting language

> PHP scripts are executed on the server

> PHP supports many databases (MySQL, Informix, Oracle, Sybase, Solid, PostgreSQL, Generic ODBC, etc.)

> PHP is open source software

> PHP is free to download and use

PHP Introduction

> PHP runs on different platforms (Windows, Linux, Unix, etc.)

> PHP is compatible with almost all servers used today (Apache, IIS, etc.)

> PHP is FREE to download from the official PHP resource: www.php.net

> PHP is easy to learn and runs efficiently on the server side

http://www.php.net/

PHP Introduction

Some info on MySQL which we will cover in the next workshop...

> MySQL is a database server

> MySQL is ideal for both small and large applications

> MySQL supports standard SQL

> MySQL compiles on a number of platforms

> MySQL is free to download and use

PHP Introduction

Instead of lots of commands to output HTML (as seen in C or Perl), PHP pages contain HTML with embedded code that does "something" (like in the next slide, it outputs "Hi, I'm a PHP script!"). The PHP code is enclosed in special start and end processing instructions <?php and ?> that allow you to jump into and out of "PHP mode."

PHP Introduction

PHP Introduction

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. A visual, if you please...

PHP Introduction

PHP Getting Started

On windows, you can download and install XAAMP. With one installation and you get an Apache webserver, database server and php.

PHP Hello World

Above is the PHP source code.

PHP Hello World

It renders as HTML that looks like this:

PHP Hello World

This program is extremely simple and you really did not need to use PHP to create a page like this. All it does is display: Hello World using the PHP echo() statement. Think of this as a normal HTML file which happens to have a set of special tags available to you that do a lot of interesting things.

PHP Comments

In PHP, we use // to make a single-line comment or /* and */ to make a large comment block.

PHP Variables

> Variables are used for storing values, like text strings, numbers or arrays.

> When a variable is declared, it can be used over and over again in your script.

> All variables in PHP start with a $ sign symbol.

> The correct way of declaring a variable in PHP:

PHP Variables

> In PHP, a variable does not need to be declared before adding a value to it.

> In the example above, you see that you do not have to tell PHP which data type the variable is.

> PHP automatically converts the variable to the correct data type, depending on its value.

PHP Variables

> A variable name must start with a letter or an underscore "_" -- not a number

> A variable name can only contain alpha-numeric characters, underscores (a-z, A-Z, 0-9, and _ )

> A variable name should not contain spaces. If a variable name is more than one word, it should be separated with an underscore ($my_string) or with capitalization ($myString)

PHP Variables Scope

PHP has three different variable scopes:

local

global

static

Local Scope

A variable declared within a function has a LOCAL SCOPE and can only be accessed within that function:

<?php function myTest() { $x = 5; // local scope echo "<p>Variable x inside function is: $x</p>"; } myTest(); // using x outside the function will generate an error echo "<p>Variable x outside function is: $x</p>"; ?>

Global Scope

A variable declared outside a function has a GLOBAL SCOPE and can only be accessed outside a function:

<?php $x = 5; // global scope function myTest() { // using x inside this function will generate an error echo "<p>Variable x inside function is: $x</p>"; } myTest(); echo "<p>Variable x outside function is: $x</p>"; ?>

PHP The global Keyword

The global keyword is used to access a global variable from within a function.

<?php $x = 5; $y = 10; function myTest() { global $x, $y; $y = $x + $y; } myTest(); echo $y; // outputs 15 ?>

Global Variables

PHP also stores all global variables in an array called $GLOBALS[index]. The index holds the name of the variable.

<?php $x = 5; $y = 10; function myTest() { $GLOBALS['y'] = $GLOBALS['x'] + $GLOBALS['y']; } myTest(); echo $y; // outputs 15 ?>

PHP The static Keyword Normally, when a function is completed/executed,

all of its variables are deleted. However, sometimes we want a local variable NOT to be deleted. We need it for a further job.

<?php function myTest() { static $x = 0; echo $x; $x++; } myTest(); myTest(); myTest(); ?>

PHP Concatenation

> The concatenation operator (.) is used to put two string values together.

> To concatenate two string variables together, use the concatenation operator:

PHP Concatenation

The output of the code on the last slide will be: If we look at the code you see that we used the concatenation operator two times. This is because we had to insert a third string (a space character), to separate the two strings.

PHP Operators

Operators are used to operate on values. There are four classifications of operators: > Arithmetic > Assignment > Comparison > Logical

PHP Operators

PHP Operators

PHP Operators

PHP Operators

PHP Conditional Statements

> Very often when you write code, you want to perform different actions for different decisions.

> You can use conditional statements in your code to do this.

> In PHP we have the following conditional statements...


> if statement - use this statement to execute some code only if a specified condition is true

> if...else statement - use this statement to execute some code if a condition is true and another code if the condition is false

> if...elseif....else statement - use this statement to select one of several blocks of code to be executed

> switch statement - use this statement to select one of many blocks of code to be executed


The following example will output "Have a nice weekend!" if the current day is Friday:


Use the if....else statement to execute some code if a condition is true and another code if a condition is false.


If more than one line should be executed if a condition is true/false, the lines should be enclosed within curly braces { }


The following example will output "Have a nice weekend!" if the current day is Friday, and "Have a nice Sunday!" if the current day is Sunday. Otherwise it will output "Have a nice day!":


Use the switch statement to select one of many blocks of code to be executed.


For switches, first we have a single expression n (most often a variable), that is evaluated once. The value of the expression is then compared with the values for each case in the structure. If there is a match, the block of code associated with that case is executed. Use break to prevent the code from running into the next case automatically. The default statement is used if no match is found.


PHP Arrays

> An array variable is a storage area holding a number or text. The problem is, a variable will hold only one value.

> An array is a special variable, which can store multiple values in one single variable.

PHP Arrays

If you have a list of items (a list of car names, for example), storing the cars in single variables could look like this:

PHP Arrays

> However, what if you want to loop through the cars and find a specific one? And what if you had not 3 cars, but 300?

> The best solution here is to use an array.

> An array can hold all your variable values under a single name. And you can access the values by referring to the array name.

> Each element in the array has its own index so that it can be easily accessed.

PHP Arrays

In PHP, there are three kind of arrays:

> Numeric array - An array with a numeric index

> Associative array - An array where each ID key is associated with a value

> Multidimensional array - An array containing one or more arrays

PHP Numeric Arrays

> A numeric array stores each array element with a numeric index.

> There are two methods to create a numeric array.

PHP Numeric Arrays

In the following example the index is automatically assigned (the index starts at 0): In the following example we assign the index manually:

PHP Numeric Arrays

In the following example you access the variable values by referring to the array name and index: The code above will output:

PHP Associative Arrays

> With an associative array, each ID key is associated with a value.

> When storing data about specific named values, a numerical array is not always the best way to do it.

> With associative arrays we can use the values as keys and assign values to them.


In this example we use an array to assign ages to the different persons: This example is the same as the one above, but shows a different way of creating the array:


PHP Multidimensional Arrays

In a multidimensional array, each element in the main array can also be an array. And each element in the sub-array can be an array, and so on.




PHP Loops

> Often when you write code, you want the same block of code to run over and over again in a row. Instead of adding several almost equal lines in a script we can use loops to perform a task like this.

> In PHP, we have the following looping statements:

PHP Loops

> while - loops through a block of code while a specified condition is true

> do...while - loops through a block of code once, and then repeats the loop as long as a specified condition is true

> for - loops through a block of code a specified number of times

> foreach - loops through a block of code for each element in an array

PHP Loops - While

The while loop executes a block of code while a condition is true. The example below defines a loop that starts with i=1. The loop will continue to run as long as i is less than, or equal to 5. i will increase by 1 each time the loop runs:

PHP Loops - While

PHP Loops – Do ... While

The do...while statement will always execute the block of code once, it will then check the condition, and repeat the loop while the condition is true. The next example defines a loop that starts with i=1. It will then increment i with 1, and write some output. Then the condition is checked, and the loop will continue to run as long as i is less than, or equal to 5:



PHP Loops - For

PHP Loops - For

Parameters:

> init: Mostly used to set a counter (but can be any code to be executed once at the beginning of the loop)

> condition: Evaluated for each loop iteration. If it evaluates to TRUE, the loop continues. If it evaluates to FALSE, the loop ends.

> increment: Mostly used to increment a counter (but can be any code to be executed at the end of the loop)

PHP Loops - For

The example below defines a loop that starts with i=1. The loop will continue to run as long as i is less than, or equal to 5. i will increase by 1 each time the loop runs:

PHP Loops - For

PHP Loops - Foreach

For every loop iteration, the value of the current array element is assigned to $value (and the array pointer is moved by one) - so on the next loop iteration, you'll be looking at the next array value.

PHP Loops - Foreach

The following example demonstrates a loop that will print the values of the given array:

PHP Loops - Foreach

PHP Functions

> We will now explore how to create your own functions.

> To keep the script from being executed when the page loads, you can put it into a function.

> A function will be executed by a call to the function.

> You may call a function from anywhere within a page.

PHP Functions

A function will be executed by a call to the function. > Give the function a name that reflects what the function does > The function name can start with a letter or underscore (not a number)

PHP Functions

A simple function that writes a name when it is called:

PHP Functions - Parameters

Adding parameters...

> To add more functionality to a function, we can add parameters. A parameter is just like a variable.

> Parameters are specified after the function name, inside the parentheses.




This example adds different punctuation.


PHP Default Argument Value

If we call the function setHeight() without arguments it takes the default value as argument:

<?php function setHeight($minheight = 50) { echo "The height is : $minheight <br>"; } setHeight(350); setHeight(); // will use the default value of 50 setHeight(135); setHeight(80); ?>

PHP Functions - Returning values

To let a function return a value, use the return statement:

<?php function sum($x, $y) { $z = $x + $y; return $z; } echo "5 + 10 = " . sum(5, 10) . "<br>"; echo "7 + 13 = " . sum(7, 13) . "<br>"; echo "2 + 4 = " . sum(2, 4); ?>

PHP Global Variables - Superglobals

Several predefined variables in PHP are

"superglobals", which means that they are always accessible, regardless of scope - and you can access them from any function, class or file without having to do anything special.

PHP superglobal variables

The PHP superglobal variables are:

$GLOBALS

$_SERVER

$_REQUEST

$_POST

$_GET

$_FILES

$_ENV

$_COOKIE

$_SESSION

PHP $GLOBALS

$GLOBALS is a PHP super global variable which is used to access global variables from anywhere in the PHP script (also from within functions or methods).

PHP stores all global variables in an array called $GLOBALS[index]. The index holds the name of the variable.

PHP $GLOBALS

Example

<?php $x = 75; $y = 25; function addition() { $GLOBALS['z'] = $GLOBALS['x'] + $GLOBALS['y']; } addition(); echo $z; ?>

PHP $_SERVER

$_SERVER is a PHP super global variable which holds information about headers, paths, and script locations.

<?php echo $_SERVER['PHP_SELF']; echo "<br>"; echo $_SERVER['SERVER_NAME']; echo "<br>"; echo $_SERVER['HTTP_HOST']; echo "<br>"; echo $_SERVER['SCRIPT_NAME']; ?>

Element/Code Description

$_SERVER['PHP_SELF'] Returns the filename of the currently

executing script

$_SERVER['SCRIPT_FILENAME'] Returns the absolute pathname of the

currently executing script

$_SERVER['SERVER_ADDR'] Returns the IP address of the host server

$_SERVER['SERVER_NAME'] Returns the name of the host server

$_SERVER['SERVER_SOFTWARE'] Returns the server identification string (such

as Apache/2.2.24)

$_SERVER['SERVER_PROTOCOL'] Returns the name and revision of the

information protocol (such as HTTP/1.1)

$_SERVER['REQUEST_METHOD'] Returns the request method used to access

the page (such as POST)

The following table lists the most important elements that can go inside $_SERVER:

PHP Forms - $_GET Function

> The built-in $_GET function is used to collect values from a form sent with method="get".

> Information sent from a form with the GET method is visible to everyone (it will be displayed in the browser's address bar) and has limits on the amount of information to send (max. 100 characters).


Notice how the URL carries the information after the file name.


The "welcome.php" file can now use the $_GET function to collect form data (the names of the form fields will automatically be the keys in the $_GET array)


> When using method="get" in HTML forms, all variable names and values are displayed in the URL.

> This method should not be used when sending passwords or other sensitive information!

> However, because the variables are displayed in the URL, it is possible to bookmark the page. This can be useful in some cases.

> The get method is not suitable for large variable values; the value cannot exceed 100 chars.

PHP Forms - $_POST Function

> The built-in $_POST function is used to collect values from a form sent with method="post".

> Information sent from a form with the POST method is invisible to others and has no limits on the amount of information to send.

> Note: However, there is an 8 Mb max size for the POST method, by default (can be changed by setting the post_max_size in the php.ini file).


And here is what the code of action.php might look like:


Apart from htmlspecialchars() and (int), it should be obvious what this does. htmlspecialchars() makes sure any characters that are special in html are properly encoded so people can't inject HTML tags or Javascript into your page. For the age field, since we know it is a number, we can just convert it to an integer which will automatically get rid of any stray characters. The $_POST['name'] and $_POST['age'] variables are automatically set for you by PHP.


When to use method="post"?

> Information sent from a form with the POST method is invisible to others and has no limits on the amount of information to send.

> However, because the variables are not displayed in the URL, it is not possible to bookmark the page.

PHP Form Validation

The Form Element

The HTML code of the form looks like this:

<form method="post" action="<?php echo htmlspecialchars($_SERVER["PHP_SELF"]);?>">

PHP Form Validation

$_SERVER["PHP_SELF"] variable?

The $_SERVER["PHP_SELF"] is a super global variable that returns the

filename of the currently executing script.

htmlspecialchars() function?

The htmlspecialchars() function converts special characters to HTML entities.

This means that it will replace HTML characters like < and > with < and >.

This prevents attackers from exploiting the code by injecting HTML or

Javascript code (Cross-site Scripting attacks) in forms.

REQUIRED FIELD if (empty($_POST["name"])) {

$nameErr = "Name is required"; } else { $name = $_POST["name"]; } DISPLAY ERROR MESSAGE

<form method="post" action="<?php echo htmlspecialchars($_SERVER["PHP_SELF"]);?>"> Name: <input type="text" name="name"> <span class="error">* <?php echo $nameErr;?></span><br>

PHP - Validate Name

$name = $_POST["name"]; if (!preg_match("/^[a-zA-Z ]*$/",$name)) { $nameErr = "Only letters and white space allowed"; }

The preg_match() function searches a string for pattern, returning true if the pattern exists, and false otherwise.

PHP - Validate E-mail

$email = $_POST["email"]; if (!filter_var($email, FILTER_VALIDATE_EMAIL)) { $emailErr = "Invalid email format"; }

The easiest and safest way to check whether an email address is well-formed is to use PHP's filter_var() function.

PHP - Validate URL

The code below shows a way to check if a URL address syntax is valid (this regular expression also allows dashes in the URL).

$website = $_POST["website"]; if (!preg_match("/\b(?:(?:https?|ftp):\/\/|www\.)[-a-z0-9+&@#\/%?=~_|!:,.;]*[-a-z0-9+&@#\/%=~_|]/i",$website)) { $websiteErr = "Invalid URL"; }

PHP And MySQL

MySQL is the most popular open-source database system.

Connecting to Database

Create a Connection to a MySQL Database

-

mysql_connect(servername,username,password);

Parameter Description

servername Optional. Specifies the server to connect to. Default value is "localhost:3306"

username Optional. Specifies the username to log in with. Default value is the name of the user that owns the server process

password Optional. Specifies the password to log in with. Default is ""

-Before you can access data in a database, you must create a connection to the database.

-In PHP, this is done with the mysql_connect() function.

Syntax

Establishing and Closing the connection

<?php $con = mysql_connect("localhost","peter","abc123"); if (!$con) { die('Could not connect: ' . mysql_error()); } // some code

mysql_close($con); ?>

die - Output a message and terminate the current script

Create a Database

CREATE DATABASE database_name

The CREATE DATABASE statement is used to create a database in MySQL.

Syntax

To get PHP to execute the statement above we must use the mysql_query() function. This function is used to send a query or command to a MySQL connection.

Create a Database <?php

$con = mysql_connect("localhost","peter","abc123"); if (!$con) { die('Could not connect: ' . mysql_error()); } if (mysql_query("CREATE DATABASE my_db",$con)) { echo "Database created"; } else { echo "Error creating database: " . mysql_error(); } mysql_close($con); ?>

Create a Table <?php

//Create database mysql_select_db("my_db", $con);//select database

//create table $sql = "CREATE TABLE Persons ( FirstName varchar(15), LastName varchar(15), Age int )"; mysql_query($sql,$con); // Execute query mysql_close($con); // Close Connection ?>

Insert Data Into a Database Table

<?php $con = mysql_connect("localhost","peter","abc123"); if (!$con) { die('Could not connect: ' . mysql_error()); }

Insert Data Into a Database Table

mysql_select_db("my_db", $con); mysql_query("INSERT INTO Persons (FirstName, LastName, Age) VALUES ('Peter', 'Griffin', 35)"); mysql_query("INSERT INTO Persons (FirstName, LastName, Age) VALUES ('Glenn', 'Quagmire', 23)"); mysql_close($con); ?>

Insert Data From a Form Into a Database

HTML form:

<html> <body> <form action="insert.php" method="post"> Firstname: <input type="text" name="firstname" /> Lastname: <input type="text" name="lastname" /> Age: <input type="text" name="age" /> <input type="submit" /> </form> </body> </html>


"insert.php" page:

<?php $con = mysql_connect("localhost","peter","abc123"); if (!$con) { die('Could not connect: ' . mysql_error()); } mysql_select_db("my_db", $con);


$sql="INSERT INTO Persons (FirstName, LastName, Age) VALUES ('$_POST[firstname]','$_POST[lastname]',

$_POST[age])";

if (!mysql_query($sql,$con)) { die('Error: ' . mysql_error()); } mysql_close($con) ?>

Select Data From a Database Table

<?php $con = mysql_connect("localhost","peter","abc123"); if (!$con) { die('Could not connect: ' . mysql_error()); } mysql_select_db("my_db", $con);

Select Data From a Database Table

$result = mysql_query("SELECT * FROM Persons"); while($row = mysql_fetch_array($result)) { echo $row['FirstName'] . " " . $row['LastName']; echo "<br />"; } mysql_close($con); ?>

Explanation

- The example stores the data returned by the mysql_query() function in the $result variable.

- mysql_fetch_array — Fetch a result row as an associative array, a numeric array, or both

- Next, we use the mysql_fetch_array() function to return the first row from the recordset as an array. Each call to mysql_fetch_array() returns the next row in the recordset. The while loop loops through all the records in the recordset.

PHP and MYSQL - … · > PHP supports many databases (MySQL, Informix, Oracle, Sybase, Solid, ... > Variables are used for storing values, like text strings, numbers or arrays.

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