Basic & workshops

All about PHP

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PHP Tutorial

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Introduction

Up until recently, scripting on the internet was something which very few people even attempted, let alone mastered. Recently though, more and more people have been building their own websites and scripting languages have become more important. Because of this, scripting languages are becomming easier to learn and PHP is one of the easiest and most powerful yet.

What Is PHP?

PHP stands for Hypertext Preprocessor and is a server-side language. This means that the script is run on your web server, not on the user's browser, so you do not need to worry about compatibility issues. PHP is relatively new (compared to languages such as Perl (CGI) and Java) but is quickly becomming one of the most popular scripting languages on the internet.

Why PHP?

You may be wondering why you should choose PHP over other languages such as Perl or even why you should learn a scripting language at all. I will deal with learning scripting languages first. Learning a scripting language, or even understanding one, can open up huge new possibilities for your website. Although you can download pre-made scripts from sites like Hotscripts, these will often contain advertising for the author or will not do exactly what you want. With an understanding of a scripting language you can easily edit these scripts to do what you want, or even create your own scripts.

Using scripts on your website allows you to add many new 'interactive' features like feedback forms, guestbooks, message boards, counters and even more advanced features like portal systems, content management, advertising managers etc. With these sort of things on your website you will find that it gives a more professional image. As well as this, anyone wanting to work in the site development industry will find that it is much easier to get a job if they know a scripting language.

What Do I Need?

As mentioned earlier, PHP is a server-side scripting language. This means that, although your users will not need to install new software, you web host will need to have PHP set up on their server. It should be listed as part of your package but if you don't know if it is installed you can find out using the first script in this tutorial. If you server does not support PHP you can ask your web host to install it for you as it is free to download and install. If you need a low cost web host which supports PHP I would recommmend HostRocket.

Writing PHP

Writing PHP on your computer is actually very simple. You don't need any specail software, except for a text editor (like Notepad in Windows). Run this and you are ready to write your first PHP script.

Declaring PHP

PHP scripts are always enclosed in between two PHP tags. This tells your server to parse the information between them as PHP. The three different forms are as follows:

<?

PHP Code In Here

?>

<?php

PHP Code In Here

php?>

<script language="php">

PHP Code In Here

</script>

All of these work in exactly the same way but in this tutorial I will be using the first option (<? and ?>). There is no particular reason for this, though, and you can use either of the options. You must remember, though, to start and end your code with the same tag (you can't start with <? and end with </script> for example).

Your First Script

The first PHP script you will be writing is very basic. All it will do is print out all the information about PHP on your server. Type the following code into your text editor:

<?

phpinfo();

?>

As you can see this actually just one line of code. It is a standard PHP function called phpinfo which will tell the server to print out a standard table of information giving you information on the setup of the server.

One other thing you should notice in this example is th

at the line ends in a semicolon. This is very important. As with many other scripting and programming languages nearly all lines are ended with a semicolon and if you miss it out you will get an error.

Finishing and Testing Your Script

Now you have finished your script save it as phpinfo.php and upload it to your server in the normal way. Now, using your browser, go the the URL of the script. If it has worked (and if PHP is installed on your server) you should get a huge page full of the information about PHP on your server.

If your script doesn't work and a blank page displays, you have either mistyped your code or your server does not support this function (although I have not yet found a server that does not). If, instead of a page being displayed, you are prompted to download the file, PHP is not installed on your server and you should either serach for a new web host or ask your current host to install PHP.

It is a good idea to keep this script for future reference.

PHP Introduction

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PHP is a server-side scripting language.

What You Should Already Know

Before you continue you should have a basic understanding of the following:

HTML/XHTML
JavaScript

If you want to study these subjects first, find the tutorials on our Home page.

What is PHP?

PHP stands for PHP: Hypertext Preprocessor
PHP is a server-side scripting language, like ASP
PHP scripts are executed on the server
PHP supports many databases (MySQL, Informix, Oracle, Sybase, Solid, PostgreSQL, Generic ODBC, etc.)
PHP is an open source software
PHP is free to download and use

What is a PHP File?

PHP files can contain text, HTML tags and scripts
PHP files are returned to the browser as plain HTML
PHP files have a file extension of ".php", ".php3", or ".phtml"

What is MySQL?

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 + MySQL

PHP combined with MySQL are cross-platform (you can develop in Windows and serve on a Unix platform)

Why PHP?

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

Where to Start?

To get access to a web server with PHP support, you can:

Install Apache (or IIS) on your own server, install PHP, and MySQL
Or find a web hosting plan with PHP and MySQL support

PHP Installation

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What do you Need?

If your server supports PHP you don't need to do anything.

Just create some .php files in your web directory, and the server will parse them for you. Because it is free, most web hosts offer PHP support.

However, if your server does not support PHP, you must install PHP.

Here is a link to a good tutorial from PHP.net on how to install PHP5: http://www.php.net/manual/en/install.php

Download PHP

Download PHP for free here: http://www.php.net/downloads.php

Download MySQL Database

Download MySQL for free here: http://www.mysql.com/downloads/

Download Apache Server

Download Apache for free here: http://httpd.apache.org/download.cgi

PHP Syntax

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PHP code is executed on the server, and the plain HTML result is sent to the browser.

Basic PHP Syntax

A PHP scripting block always starts with <?php and ends with ?>. A PHP scripting block can be placed anywhere in the document.

On servers with shorthand support enabled you can start a scripting block with <? and end with ?>.

For maximum compatibility, we recommend that you use the standard form (<?php) rather than the shorthand form.

<?php

?>

A PHP file normally contains HTML tags, just like an HTML file, and some PHP scripting code.

Below, we have an example of a simple PHP script which sends the text "Hello World" to the browser:

Each code line in PHP must end with a semicolon. The semicolon is a separator and is used to distinguish one set of instructions from another.

There are two basic statements to output text with PHP: echo and print. In the example above we have used the echo statement to output the text "Hello World".

Note: The file must have a .php extension. If the file has a .html extension, the PHP code will not be executed.

Comments in PHP

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

PHP Variables

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A variable is used to store information.

Variables in PHP

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:

$var_name = value;

New PHP programmers often forget the $ sign at the beginning of the variable. In that case it will not work.

Let's try creating a variable containing a string, and a variable containing a number:

<?php

$txt="Hello World!";

$x=16;

?>

PHP is a Loosely Typed Language

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.

In a strongly typed programming language, you have to declare (define) the type and name of the variable before using it.

In PHP, the variable is declared automatically when you use it.

Naming Rules for Variables

A variable name must start with a letter or an underscore "_"
A variable name can only contain alpha-numeric characters and 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 String Variables

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A string variable is used to store and manipulate text.

String Variables in PHP

String variables are used for values that contain characters.

In this chapter we are going to look at the most common functions and operators used to manipulate strings in PHP.

After we create a string we can manipulate it. A string can be used directly in a function or it can be stored in a variable.

Below, the PHP script assigns the text "Hello World" to a string variable called $txt:

<?php

$txt="Hello World";

echo $txt;

?>

The output of the code above will be:

Hello World

Now, lets try to use some different functions and operators to manipulate the string.

The Concatenation Operator

There is only one string operator in PHP.

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

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

<?php

$txt1="Hello World!";

$txt2="What a nice day!";

echo $txt1 . " " . $txt2;

?>

The output of the code above will be:

Hello World! What a nice day!

If we look at the code above 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.

The strlen() function

The strlen() function is used to return the length of a string.

Let's find the length of a string:

<?php

echo strlen("Hello world!");

?>

The output of the code above will be:

The length of a string is often used in loops or other functions, when it is important to know when the string ends. (i.e. in a loop, we would want to stop the loop after the last character in the string).

The strpos() function

The strpos() function is used to search for a character/text within a string.

If a match is found, this function will return the character position of the first match. If no match is found, it will return FALSE.

Let's see if we can find the string "world" in our string:

<?php

echo strpos("Hello world!","world");

?>

The output of the code above will be:

The position of the string "world" in the example above is 6. The reason that it is 6 (and not 7), is that the first character position in the string is 0, and not 1.

Complete PHP String Reference

For a complete reference of all string functions, go to our complete PHP String Reference.

The reference contains a brief description, and examples of use, for each function!

PHP Operators

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Operators are used to operate on values.

PHP Operators

This section lists the different operators used in PHP.

Arithmetic Operators

Operator	Description	Example	Result
+	Addition	x=2 x+2	4
-	Subtraction	x=2 5-x	3
*	Multiplication	x=4 x*5	20
/	Division	15/5 5/2	3 2.5
%	Modulus (division remainder)	5%2 10%8 10%2	1 2 0
++	Increment	x=5 x++	x=6
--	Decrement	x=5 x--	x=4

Assignment Operators

Operator	Example	Is The Same As
=	x=y	x=y
+=	x+=y	x=x+y
-=	x-=y	x=x-y
*=	x*=y	x=x*y
/=	x/=y	x=x/y
.=	x.=y	x=x.y
%=	x%=y	x=x%y

Comparison Operators

Operator	Description	Example
==	is equal to	5==8 returns false
!=	is not equal	5!=8 returns true
<>	is not equal	5<>8 returns true
>	is greater than	5>8 returns false
<	is less than	5<8 returns true
>=	is greater than or equal to	5>=8 returns false
<=	is less than or equal to	5<=8 returns true

Logical Operators

Operator	Description	Example
&&	and	x=6 y=3 (x < 10 && y > 1) returns true
\|\|	or	x=6 y=3 (x==5 \|\| y==5) returns false
!	not	x=6 y=3 !(x==y) returns true

PHP If...Else Statements

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Conditional statements are used to perform different actions based on different conditions.

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 if Statement

Use the if statement to execute some code only if a specified condition is true.

Syntax

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

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

Notice that there is no ..else.. in this syntax. The code is executed only if the specified condition is true.

The if...else Statement

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

Syntax

if (condition)

code to be executed if condition is true;

else

code to be executed if condition is false;

Example

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

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

<html>

<body>

<?php

$d=date("D");

if ($d=="Fri")

  {

  echo "Hello!<br />";

  echo "Have a nice weekend!";

  echo "See you on Monday!";

  }

?>

</body>

</html>

The if...elseif....else Statement

Use the if....elseif...else statement to select one of several blocks of code to be executed.

Syntax

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;

Example

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!":

PHP Switch Statement

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Conditional statements are used to perform different actions based on different conditions.

The PHP Switch Statement

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

Syntax

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;

}

This is how it works: 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.

Example

PHP Arrays

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An array stores multiple values in one single variable.

What is an Array?

A 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.

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

$cars1="Saab";

$cars2="Volvo";

$cars3="BMW";

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.

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

Numeric Arrays

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

There are two methods to create a numeric array.

1. In the following example the index are automatically assigned (the index starts at 0):

$cars=array("Saab","Volvo","BMW","Toyota");

2. In the following example we assign the index manually:

$cars[0]="Saab";

$cars[1]="Volvo";

$cars[2]="BMW";

$cars[3]="Toyota";

Example

In the following example you access the variable values by referring to the array name and index:

<?php

$cars[0]="Saab";

$cars[1]="Volvo";

$cars[2]="BMW";

$cars[3]="Toyota";

echo $cars[0] . " and " . $cars[1] . " are Swedish cars.";

?>

The code above will output:

Saab and Volvo are Swedish cars.

Associative Arrays

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.

Example 1

In this example we use an array to assign ages to the different persons:

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

Example 2

This example is the same as example 1, but shows a different way of creating the array:

$ages['Peter'] = "32";

$ages['Quagmire'] = "30";

$ages['Joe'] = "34";

The ID keys can be used in a script:

<?php

$ages['Peter'] = "32";

$ages['Quagmire'] = "30";

$ages['Joe'] = "34";

echo "Peter is " . $ages['Peter'] . " years old.";

?>

The code above will output:

Peter is 32 years old.

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.

Example

In this example we create a multidimensional array, with automatically assigned ID keys:

$families = array

  (

  "Griffin"=>array

  (

  "Peter",

  "Lois",

  "Megan"

  ),

  "Quagmire"=>array

  (

  "Glenn"

  ),

  "Brown"=>array

  (

  "Cleveland",

  "Loretta",

  "Junior"

  )

  );

The array above would look like this if written to the output:

Array

(

[Griffin] => Array

  (

  [0] => Peter

  [1] => Lois

  [2] => Megan

  )

[Quagmire] => Array

  (

  [0] => Glenn

  )

[Brown] => Array

  (

  [0] => Cleveland

  [1] => Loretta

  [2] => Junior

  )

)

Example 2

Lets try displaying a single value from the array above:

echo "Is " . $families['Griffin'][2] .

" a part of the Griffin family?";

The code above will output:

Is Megan a part of the Griffin family?

Complete PHP Array Reference

For a complete reference of all array functions, go to our complete PHP Array Reference.

The reference contains a brief description, and examples of use, for each function!

PHP Looping - While Loops

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Loops execute a block of code a specified number of times, or while a specified condition is true.

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:

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

The while Loop

The while loop executes a block of code while a condition is true.

Syntax

while (condition)

{

code to be executed;

}

Example

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:

Output:

The number is 1

The number is 2

The number is 3

The number is 4

The number is 5

The do...while Statement

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.

Syntax

do

{

code to be executed;

}

while (condition);

Example

The example below 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:

<html>

<body>

<?php

$i=1;

do

  {

  $i++;

  echo "The number is " . $i . "<br />";

  }

while ($i<=5);

?>

</body>

</html>

Output:

The number is 2

The number is 3

The number is 4

The number is 5

The number is 6

The for loop and the foreach loop will be explained in the next chapter.

PHP Looping - For Loops

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Loops execute a block of code a specified number of times, or while a specified condition is true.

The for Loop

The for loop is used when you know in advance how many times the script should run.

Syntax

for (init; condition; increment)

{

code to be executed;

}

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)

Note: Each of the parameters above can be empty, or have multiple expressions (separated by commas).

Example

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:

Output:

The number is 1

The number is 2

The number is 3

The number is 4

The number is 5

The foreach Loop

The foreach loop is used to loop through arrays.

Syntax

foreach ($array as $value)

{

code to be executed;

}

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.

Example

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

Output:

one

two

three

PHP Functions

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The real power of PHP comes from its functions.

In PHP, there are more than 700 built-in functions.

PHP Built-in Functions

For a complete reference and examples of the built-in functions, please visit our PHP Reference.

PHP Functions

In this chapter we will show you 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.

Create a PHP Function

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

Syntax

function functionName()

{

code to be executed;

}

PHP function guidelines:

Give the function a name that reflects what the function does
The function name can start with a letter or underscore (not a number)

Example

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

Output:

My name is Kai Jim Refsnes

PHP Functions - 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.

Example 1

The following example will write different first names, but equal last name:

<html>

<body>

<?php

function writeName($fname)

{

echo $fname . " Refsnes.<br />";

}

echo "My name is ";

writeName("Kai Jim");

echo "My sister's name is ";

writeName("Hege");

echo "My brother's name is ";

writeName("Stale");

?>

</body>

</html>

Output:

My name is Kai Jim Refsnes.

My sister's name is Hege Refsnes.

My brother's name is Stale Refsnes.

Example 2

The following function has two parameters:

<html>

<body>

<?php

function writeName($fname,$punctuation)

{

echo $fname . " Refsnes" . $punctuation . "<br />";

}

echo "My name is ";

writeName("Kai Jim",".");

echo "My sister's name is ";

writeName("Hege","!");

echo "My brother's name is ";

writeName("Ståle","?");

?>

</body>

</html>

Output:

My name is Kai Jim Refsnes.

My sister's name is Hege Refsnes!

My brother's name is Ståle Refsnes?

PHP Functions - Return values

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

Example

Output:

1 + 16 = 17

PHP Forms and User Input

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The PHP $_GET and $_POST variables are used to retrieve information from forms, like user input.

PHP Form Handling

The most important thing to notice when dealing with HTML forms and PHP is that any form element in an HTML page will automatically be available to your PHP scripts.

Example

The example below contains an HTML form with two input fields and a submit button:

When a user fills out the form above and click on the submit button, the form data is sent to a PHP file, called "welcome.php":

"welcome.php" looks like this:

<html>

<body>

Welcome <?php echo $_POST["fname"]; ?>!<br />

You are <?php echo $_POST["age"]; ?> years old.

</body>

</html>

Output could be something like this:

Welcome John!

You are 28 years old.

The PHP $_GET and $_POST variables will be explained in the next chapters.

Form Validation

User input should be validated on the browser whenever possible (by client scripts). Browser validation is faster and reduces the server load.

You should consider server validation if the user input will be inserted into a database. A good way to validate a form on the server is to post the form to itself, instead of jumping to a different page. The user will then get the error messages on the same page as the form. This makes it easier to discover the error.

PHP $_GET Variable

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In PHP, the predefined $_GET variable is used to collect values in a form with method="get".

The $_GET Variable

The predefined $_GET variable is used to collect values in a form 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.

Example

When the user clicks the "Submit" button, the URL sent to the server could look something like this:

http://www.w3schools.com/welcome.php?fname=Peter&age=37

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

Welcome <?php echo $_GET["fname"]; ?>.<br />

You are <?php echo $_GET["age"]; ?> years old!

When to use method="get"?

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

Note: 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.

Note: The get method is not suitable for very large variable values. It should not be used with values exceeding 2000 characters.

PHP $_POST Function

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In PHP, the predefined $_POST variable is used to collect values in a form with method="post".

The $_POST Variable

The predefined $_POST variable 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).

Example

When the user clicks the "Submit" button, the URL will look like this:

http://www.w3schools.com/welcome.php

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

Welcome <?php echo $_POST["fname"]; ?>!<br />

You are <?php echo $_POST["age"]; ?> years old.

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.

The PHP $_REQUEST Variable

The predefined $_REQUEST variable contains the contents of both $_GET, $_POST, and $_COOKIE.

The $_REQUEST variable can be used to collect form data sent with both the GET and POST methods.

Example

Welcome <?php echo $_REQUEST["fname"]; ?>!<br />

You are <?php echo $_REQUEST["age"]; ?> years old.