Info: PHP Tutorial Part 1 - Overclock.net

xxmonkey321xx · 09-19-06

PHP Tutorial

Welcome to the basic PHP tutorial. You will be learning the following items:

Opening/Closing Tags
Comments (//, #, and /* */)
Variables
Echo
If/elseif/else
$_POST and $_GET
Switch
Function
Arrays
Basic MySQL connectivity
Include

You will need:

Apache HTTP Server, Installed with PHP working
MySQL Installed (only if you want to learn how to connect to it)
Patience
Caffine

Ok, here we go...

Tags surround EVERY PHP script. The tags are <?php for opening, and ?> for closing.

An example:

PHP Code:


			
<?php



Script here



?>

Comments

It is possible to add comments to scripts, such as your name and a copyright notice, as so:

PHP Code:


			
<?php

########################

# This is a comment    #

# And catches your eye #

########################



#This is a comment along with everything else on this line



//This is a comment along with everything else on this line.



/* This is a comment along with everything else between the asterisks and slashes */



This line is not a comment



?>

Variables

Let's start with Variables, since they are rather basic and easy to learn.

A few examples of variables:

PHP Code:


			
<?php



$var = "hello";

$var2 = "world";

$var3 = " ";



//NOTICE that each line has a semicolon after it!! You much have a semicolon after EACH AND EVERY separate command.



//Lets combine these variables:



$combined = $var . $var3 . $var2;



//If we were to echo $combined, it would look like "hello world" (without quotes). The periods signify combining.



?>

Variables can be names anything, they just have to start with a $. So $asdkskla is a variable, $hello is a variable and so on.

Echoing

Let's move on to echo.

Echo is a very simple print, spitting out whatever you tell it to.

For example:

PHP Code:


			
<?php



$hello world = "Hello World"; //THIS WOULD MAKE AN ERROR!!! There is a space in the variable name, which is not allowed.



$hello_world = "Hello World";



$number = 42; //No quotes needed since this is a single number(no spaces)



$number2 = $number; //Therefore $number2 is the same as whatever $number is



$html = "<a href="http://www.overclock.net">Awesome Site</a>";



//So let's echo, shall we?



echo "Hello World!"; //Echoes what is in quotes, in this case "Hello World!"



echo $hello_world; //Echoes variable $hello_world, which is set to "Hello World!"



echo $number; //Will echo variable $number, which is set to 42



echo $number . $number2; //Will echo 4242 nice both $number and $number2 are set to 42



echo $html; // Would echo HTML code which the browser will interpret, and turn into a link in this case.



?>

If/IfElse/Else

You can setup if/else command rather easy. These are handy if you want to check what is input against hat you have in your database, along with some other uses.

A basic if/else command looks like this:

PHP Code:


			
<?php



if ($variable == $other_var) {



// Code to execute



}

elseif($vaiable == $another_var) {



// Code to execute



}

else {



// Code to execute if both if and ifelse(s) all fail. (Last-resort sort of thing)



};

?>

So let's say we have a variable, $input, and we want to check it for age (it's a number). You can make it as a cheap password to get into a section of your site, but this is not recommended.

PHP Code:


			
<?php



$input = "42";



if ($input == 42) {



echo "The number is correct! Blah blah...";



}

else{



echo "The number is incorrect!";



};



?>

Elseif's are rarely used, since normally you can sum it all up in one if statement.

$_POST and $_GET

POST and GET retrieve information either from forms or from the link itself.

POST gets info from forms, such as username and password. Suppose you had a simple HTML form like so:

Code:

<html>
<head><title>Form</title></head>
<body>

<form name=form method=POST action=script.php>
Username: <input type=text name=username><br>
Password: <input type=password name=pass><br>
<input type=submit value="Login!">
</form>

</body>
</html>

You MUST name the input fields to get info from them.

So, to retrieve the data in that form, you would use $_POST as shown:

PHP Code:


			
<?php



$username = $_POST['username']; //you must include the single quotes! the text in the single quotes is the name of your form's input.

$password = $_POST['pass'];



echo $username; // Would echo whatever was in the username field

echo $password; // Would echo whatever was in the password field



?>

$_GET is slightly different. It comes in handy when you are using the switch command, which I will go over next.

For example, lets take an example URL:

Code:

http://www.overclock.net/showtopic.php?t=1337

t=1337 is a variable stored (out in the open) in the URL. This can be grabbed by programs and tells them what to do or what to look for, or some other things.

Say you have a PHP program that looks like this:

PHP Code:


			
<?php



if (isset($_GET['act'])) {



$var = $_GET['act'];

echo $var; //echoes whatever is stored in http://www.example.com/script.php?act=[what is stored here]

}

else{



echo "No variable present in 'act'"; 



};

?>

open this script up and you should get "No variable present in 'act'" on the screen.

Now go to your script like so:

Code:

name.php?act=test

Now it should echo "test".

Like I said before this comes in handy with switch, which you will learn in a second!

****

OK, coffee break.. or whatever, just let you brain rest for a second, to absorb all the wonderful code! Continue whenever you are ready!

****

Switch(s)

A switch is generally a fancy if/else. They come in handy for GET variables. An example of a good usage for switch is:

PHP Code:


			
<?php



switch(@$_GET['act']) {



case "login";



//Login code



break; //REQUIRED at the end of every CASE, not default!









case "logout";



//Logout code, skips over login code since act is set to logout.



break;







default:



//What happens by default if $_GET is unset or is set to something that there is no case command.



};



?>

Don't forget the @ sign, it helps to ward off errors due to strange programming glitches.

Fun with Functions

Functions come in handy if you do a certain thing a lot, like append something to the end of a variable or filename.

You can make a function and call to it at any point after it has been created.

An Example:

PHP Code:


			
<?php



function FUCNTIONNAME(optional_var1,optional_var2){



//Code



};



FUNCTIONNAME(var,var);

?>

Note that both FUNCTIONNAMEs are all capitals, since PHP is very case sensitive. $t is not the same as $T, as functionname is not the same as FUNCTIONNAME.

A Better example, to append "lmao" to the net of a string:

[PHP<?

function lmao($string) {

echo $string . "lmao";

};

lmao("Look as this, "); //Echoes Look at this, lmao

?> [/PHP]

You can also use a function to append random characters to a filename, using arrays.

Arrays

Arrays store information. Whether it is a little information or a lot, you can use arrays.

Some examples of arrays are:

PHP Code:


			
<?php



$example = array("This", "is", "an", "example");



echo $example[0]; //Echoes "This" (no quotes)





/* Example with different entries with names... */



$example2 = array("word" => "Hello", "number" => "42", "decimal" => ".7777");



echo "{$example2[word]}, the number is {$example2[number]}" . $example2[decimal]; // Echoes "Hello, the number is 42.7777" (no quotes)



?>

The Curly Brackets ({ and }) are there to tell PHP that you are accessing a variable, so it does not have a conniption when it sees some random brackets ([ and ]).

Basic MySQL connectivity

To connect to a MySQL database you need an address, a username, a password, and a database to connect to. Let's say that for this example, the host(or address) is localhost, the username is root, and the password is toor, though this may not reflect you current settings (or mine, so don't try it).

So, lets set these values as variables, and connect to MySQL!

PHP Code:


			
<?php



$host = "localhost";

$user = "root";

$pass = "toor";

$db = "test";



// Now let's connect!



mysql_connect($host, $user, $pass) or die ("Could not connect to MySQL database!"); //This means if the connection fails with will echo what is in die()



// Ok, now we are connected! Let's select a database



mysql_select_db($db) or die("Could not connect to database!");



//Now we are in the database "test"! We can run queries(ask for information) for the tables in the database!

//I like to do it like this:



$sql = "SELECT col FROM table"; //This will select the column "col" from table "table" when executed. Lets say that there is one row in this column, with an entry of "Hello World" (old, I know..)



$result = mysql_query($sql) or die("Could not execute query!");



echo $result; //Echoes Hello World



?>

But what if there is more than one row in the column? Here is how you echo them all(simply):

PHP Code:


			
<?php



$host = "localhost";

$user = "root";

$pass = "toor";

$db = "test";



mysql_connect($host, $user, $pass) or die ("Could not connect to MySQL database!");



mysql_select_db($db) or die("Could not connect to database!");



$sql = "SELECT * FROM table";



$result = mysql_query($sql) or die("Could not execute query!");



//Now for the fun part..



while($row = mysql_fetch_array($result, MYSQL_ASSOC)){



echo "{$row[col]} <br>" //Would echo each value in column "col" on a new line



};

?>

Includes

Including file is good to hide MySQL connection info and other connection info.

An example for MySQL is this: say you have the connection info in <basedir>/db/db.inc, and you want to get to it..

PHP Code:


			
<?php



include("db/db.inc"); // Adds the info in db/db.inc into the current file, just like you had typed it in



//connect to MySQL, blah blah... not it has the connection info.



mysql_connect($host, $user, $pass) or die ("Could not connect to MySQL database!");



?>

It can also be helpful to store files outside of the viewable web server, such as outside of HTDOCS holder or WWW folder, depending on what you use. You can include these too like:

PHP Code:


			
<?php

// Lets say you are in /Apache2/htdocs/program/code/ and you want to get to something in /apache2/path/to/file.extention ...

include("../../../path/to/file.extention");



// Ok, so the first ../ brings you back to the program directory, the second brings you to htdocs, and the third brings you outside of htdocs, in apache2. It's that simple!



?>

And that's it for this FAQ.. basic PHP for beginners

I hope you like it, stay tuned for Part 2!

-Monkey

drummer4lifex · 09-29-06

Great FAQ! I've always wondered where to start with PHP. This answered those questions. Also, it's not too far off from java in certain ways, but it seems to me that most programming is the same with just different syntax, functions, and managed/unmanaged memory allocation. Hopefully it's true so I can learn more languages than java (which I know very little).

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