PHP Tutorial - PHP INTRODUCTION AND ADVANCE
PHP Tutorial - Learn PHP
If you want to learn the basics of PHP, then you've come to the right place. The goal of this tutorial is to teach you the basics of PHP so that you can:
• Customize PHP scripts that you download, so that they better fit your needs.
• Begin to understand the working model of PHP, so you may begin to design your own PHP projects.
• Give you a solid base in PHP, so as to make you more valuable in the eyes of future employers.
PHP stands for PHP Hypertext Preprocessor.
PHP - What is it?
Taken directly from PHP's home, PHP.net, "PHP is an HTML-embedded scripting language. Much of its syntax is borrowed from C, Java and Perl with a couple of unique PHP-specific features thrown in. The goal of the language is to allow web developers to write dynamically generated pages quickly."
This is generally a good definition of PHP. However, it does contain a lot of terms you may not be used to. Another way to think of PHP is a powerful, behind the scenes scripting language that your visitors won't see!
When someone visits your PHP webpage, your web server processes the PHP code. It then sees which parts it needs to show to visitors(content and pictures) and hides the other stuff(file operations, math calculations, etc.) then translates your PHP into HTML. After the translation into HTML, it sends the webpage to your visitor's web browser.
PHP - What's it do?
It is also helpful to think of PHP in terms of what it can do for you. PHP will allow you to:
• Reduce the time to create large websites.
• Create a customized user experience for visitors based on information that you have gathered from them.
• Open up thousands of possibilities for online tools. Check out PHP - HotScripts for examples of the great things that are possible with PHP.
• Allow creation of shopping carts for e-commerce websites.
What You Should Know
Before starting this tutorial it is important that you have a basic understanding and experience in the following:
• HTML - Know the syntax and especially HTML Forms.
• Basic programming knowledge - This isn't required, but if you have any traditional programming experience it will make learning PHP a great deal easier.
Tutorial Overview
This tutorial is aimed at the PHP novice and will teach you PHP from the ground up. If you want a drive-through PHP tutorial this probably is not the right tutorial for you.
Remember, you should not try to plow through this tutorial in one sitting. Read a couple lessons, take a break, then do some more after the information has had some time to sink in.
PHP - Syntax
Before we talk about PHP's syntax, let us first define what syntax is referring to.
• Syntax - The rules that must be followed to write properly structured code.
PHP's syntax and semantics are similar to most other programming languages (C, Java, Perl) with the addition that all PHP code is contained with a tag, of sorts. All PHP code must be contained within the following...
PHP Code:
<?php
?>
or the shorthand PHP tag that requires shorthand support to be enabled
on your server...
<?
?>
If you are writing PHP scripts and plan on distributing them, we suggest that you use the standard form (which includes the ?php) rather than the shorthand form. This will ensure that your scripts will work, even when running on other servers with different settings.
How to Save Your PHP Pages
If you have PHP inserted into your HTML and want the web browser to interpret it correctly, then you must save the file with a .php extension, instead of the standard .html extension. So be sure to check that you are saving your files correctly. Instead of index.html, it should be index.php if there is PHP code in the file.
Example Simple HTML & PHP Page
Below is an example of one of the easiest PHP and HTML page that you can create and still follow web standards.
PHP and HTML Code:
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<html>
<head>
<title>My First PHP Page</title>
</head>
<body>
<?php
echo "Hello World!";
?>
</body>
</html>
Display:
Hello World!
If you save this file and place it on PHP enabled server and load it up in your web browser, then you should see "Hello World!" displayed. If not, please check that you followed our example correctly.
We used the PHP function echo to write "Hello World!" and we will be talking in greater depth about this PHP function and many others later on in this tutorial.
The Semicolon!
As you may or may not have noticed in the above example, there was a semicolon after the line of PHP code. The semicolon signifies the end of a PHP statement and should never be forgotten. For example, if we repeated our "Hello World!" code several times, then we would need to place a semicolon at the end of each statement.
PHP and HTML Code:
<html>
<head>
<title>My First PHP Page</title>
</head>
<body>
<?php
echo "Hello World! ";
echo "Hello World! ";
echo "Hello World! ";
echo "Hello World! ";
echo "Hello World! ";
?>
</body>
</html>
Display:
Hello World! Hello World! Hello World! Hello World! Hello World!
White Space
As with HTML, whitespace is ignored between PHP statements. This means it is OK to have one line of PHP code, then 20 lines of blank space before the next line of PHP code. You can also press tab to indent your code and the PHP interpreter will ignore those spaces as well.
PHP and HTML Code:
<html>
<head>
<title>My First PHP Page</title>
</head>
<body>
<?php
echo "Hello World!";
echo "Hello World!";
?>
</body>
</html>
Display:
Hello World!Hello World!
This is perfectly legal PHP code.
PHP - Variables
If you have never had any programming, Algebra, or scripting experience, then the concept of variables might be a new concept to you. A detailed explanation of variables is beyond the scope of this tutorial, but we've included a refresher crash course to guide you.
A variable is a means of storing a value, such as text string "Hello World!" or the integer value 4. A variable can then be reused throughout your code, instead of having to type out the actual value over and over again. In PHP you define a variable with the following form:
• $variable_name = Value;
If you forget that dollar sign at the beginning, it will not work. This is a common mistake for new PHP programmers!
A Quick Variable Example
Say that we wanted to store the values that we talked about in the above paragraph. How would we go about doing this? We would first want to make a variable name and then set that equal to the value we want. See our example below for the correct way to do this.
PHP Code:
<?php
$hello = "Hello World!";
$a_number = 4;
$anotherNumber = 8;
?>
Note for programmers: PHP does not require variables to be declared before being initialized.
PHP Variable Naming Conventions
There are a few rules that you need to follow when choosing a name for your PHP variables.
• PHP variables must start with a letter or underscore "_".
• PHP variables may only be comprised of alpha-numeric characters and underscores. a-z, A-Z, 0-9, or _ .
• Variables with more than one word should be separated with underscores. $my_variable
• Variables with more than one word can also be distinguished with capitalization. $myVariable
PHP - Echo
As you saw in the previous lesson, the PHP function echo is a means of outputting text to the web browser. Throughout your PHP career you will be using the echo function more than any other. So let's give it a solid perusal!
Outputting a String
To output a string, like we have done in previous lessons, use the PHP echo function. You can place either a string variable or you can use quotes, like we do below, to create a string that the echo function will output.
PHP Code:
<?php
$myString = "Hello!";
echo $myString;
echo "<h5>I love using PHP!</h5>";
?>
Display:
Hello!
I love using PHP!
In the above example we output "Hello!" without a hitch. The text we are outputting is being sent to the user in the form of a web page, so it is important that we use proper HTML syntax!
In our second echo statement we use echo to write a valid Header 5 HTML statement. To do this we simply put the <h5> at the beginning of the string and closed it at the end of the string. Just because you're using PHP to make web pages does not mean you can forget about HTML syntax!
Careful When Echoing Quotes!
It is pretty cool that you can output HTML with PHP. However, you must be careful when using HTML code or any other string that includes quotes! The echo function uses quotes to define the beginning and end of the string, so you must use one of the following tactics if your string contains quotations:
• Don't use quotes inside your string
• Escape your quotes that are within the string with a slash. To escape a quote just place a slash directly before the quotation mark, i.e. \"
• Use single quotes (apostrophes) for quotes inside your string.
See our example below for the right and wrong use of the echo function:
PHP Code:
<?php
// This won't work because of the quotes around specialH5!
echo "<h5 class="specialH5">I love using PHP!</h5>";
// OK because we escaped the quotes!
echo "<h5 class=\"specialH5\">I love using PHP!</h5>";
// OK because we used an apostrophe '
echo "<h5 class='specialH5'>I love using PHP!</h5>";
?>
If you want to output a string that includes quotations, either use an apostrophe ( ' ) or escape the quotations by placing a slash in front of it ( \" ). The slash will tell PHP that you want the quotation to be used within the string and NOT to be used to end echo's string.
Echoing Variables
Echoing variables is very easy. The PHP developers put in some extra work to make the common task of echoing all variables nearly foolproof! No quotations are required, even if the variable does not hold a string. Below is the correct format for echoing a variable.
PHP Code:
<?php
$my_string = "Hello Bob. My name is: ";
$my_number = 4;
$my_letter = a;
echo $my_string;
echo $my_number;
echo $my_letter;
?>
Display:
Hello Bob. My name is: 4a
Echoing Variables and Text Strings
You can also combine text strings and variables. By doing such a conjunction you save yourself from having to do a large number of echo statements. Variables and text strings are joined together with a period( . ). The example below shows how to do such a combination.
PHP Code:
<?php
$my_string = "Hello Bob. My name is: ";
$newline = "<br />";
echo $my_string."Bobettta".$newline;
echo "Hi, I'm Bob. Who are you? ".$my_string.$newline;
echo "Hi, I'm Bob. Who are you? ".$my_string."Bobetta";
?>
Display:
Hello Bob. My name is: Bobetta Hi, I'm Bob. Who are you? Hello Bob. My name is: Hi, I'm Bob. Who are you? Hello Bob. My name is: Bobetta
This combination can be done multiple times, as the example shows. This method of joining two or more strings together is called concatenation and we will talk more about this and other forms of string manipulation in our string lesson.
PHP - Strings
In the last lesson, PHP Echo, we used strings a bit, but didn't talk about them in depth. Throughout your PHP career you will be using strings a great deal, so it is important to have a basic understanding of PHP strings.
PHP - String Creation
Before you can use a string you have to create it! A string can be used directly in a function or it can be stored in a variable. Below we create the exact same string twice: first storing it into a variable and in the second case we place the string directly into a function.
PHP Code:
$my_string = "Tizag - Unlock your potential!";
echo "Tizag - Unlock your potential!";
echo $my_string;
In the above example the first string will be stored into the variable $my_string, while the second string will be used in the echo function and not be stored. Remember to save your strings into variables if you plan on using them more than once! Below is the output from our example code. They look identical just as we thought.
Display:
Tizag - Unlock your potential! Tizag - Unlock your potential!
PHP - String Creation Single Quotes
Thus far we have created strings using double-quotes, but it is just as correct to create a string using single-quotes, otherwise known as apostrophes.
PHP Code:
$my_string = 'Tizag - Unlock your potential!';
echo 'Tizag - Unlock your potential!';
echo $my_string;
If you want to use a single-quote within the string you have to escape the single-quote with a backslash \ . Like this: \' !
PHP Code:
echo 'Tizag - It\'s Neat!';
PHP - String Creation Double-Quotes
We have used double-quotes and will continue to use them as the primary method for forming strings. Double-quotes allow for many special escaped characters to be used that you cannot do with a single-quote string. Once again, a backslash is used to escape a character.
PHP Code:
$newline = "A newline is \n";
$return = "A carriage return is \r";
$tab = "A tab is \t";
$dollar = "A dollar sign is \$";
$doublequote = "A double-quote is \"";
Note: If you try to escape a character that doesn't need to be, such as an apostrophe, then the backslash will show up when you output the string.
These escaped characters are not very useful for outputting to a web page because HTML ignore extra white space. A tab, newline, and carriage return are all examples of extra (ignorable) white space. However, when writing to a file that may be read by human eyes these escaped characters are a valuable tool!
PHP - String Creation Heredoc
The two methods above are the traditional way to create strings in most programming languages. PHP introduces a more robust string creation tool called heredoc that lets the programmer create multi-line strings without using quotations. However, creating a string using heredoc is more difficult and can lead to problems if you do not properly code your string! Here's how to do it:
PHP Code:
$my_string = <<<TEST
Tizag.com
Webmaster Tutorials
Unlock your potential!
TEST;
echo $my_string;
There are a few very important things to remember when using heredoc.
• Use <<< and some identifier that you choose to begin the heredoc. In this example we chose TEST as our identifier.
• Repeat the identifier followed by a semicolon to end the heredoc string creation. In this example that was TEST;
• The closing sequence TEST; must occur on a line by itself and cannot be indented!
Another thing to note is that when you output this multi-line string to a web page, it will not span multiple lines because we did not have any <br /> tags contained inside our string! Here is the output made from the code above.
Display:
Tizag.com Webmaster Tutorials Unlock your potential!
Once again, take great care in following the heredoc creation guidelines to avoid any headaches.
PHP - Operators
In all programming languages, operators are used to manipulate or perform operations on variables and values. You have already seen the string concatenation operator "." in the Echo Lesson and the assignment operator "=" in pretty much every PHP example so far.
There are many operators used in PHP, so we have separated them into the following categories to make it easier to learn them all.
• Assignment Operators
• Arithmetic Operators
• Comparison Operators
• String Operators
• Combination Arithmetic & Assignment Operators
Assignment Operators
Assignment operators are used to set a variable equal to a value or set a variable to another variable's value. Such an assignment of value is done with the "=", or equal character. Example:
• $my_var = 4;
• $another_var = $my_var
Now both $my_var and $another_var contain the value 4. Assignments can also be used in conjunction with arithmetic operators.
Arithmetic Operators
Operator English Example
+ Addition 2 + 4
- Subtraction 6 - 2
* Multiplication 5 * 3
/ Division 15 / 3
% Modulus 43 % 10
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