PHP Programming

Variables in PHP do not need to be declared like some languages (e.g. JavaScript).

This is all that needs to be done to assign a variable:

$variable = "Value";

In php mathmatical operations treat null like 0, so any number plus null equals itself.

For example

#!/usr/local/bin/php

printf ("%d\n", null+6);

printf ("%d\n", 6+null);

?>

output:

6

6

No, ASAX is for ASP.NET, which is another language.

Have a session_start(); at the very top of the page in php like this:

<?php

session_start();

?>

Then write a login form:

<form action="login.php" method = "POST">

<input type = "text" name = "username">

<input type = "password" name = "password">

<input type = "submit" value = "submit">

</form>

now start a new page called login.php. Put session_start(); at the top of the page again. Now you'll have two different $_POST variables from the form that got submitted. It's $_POST['username'] and $_POST['password']. the "name" of the input is what the $_POST variable is. And it's a $_POST because of the method of the form. Now you should change the names of the $_POST just to make it easier.

<?php

$username = $_POST['username'];

$password = $_POST['password'];

?>

Now it's time to see if that username and password are in the database

<?php

$mysql = "SELECT COUNT(*) FROM users WHERE username = '$username' AND password = '$password'"; // Select statement to find user

$query = mysql_query($mysql); // Query to see if user exists

$result = mysql_query($query); // Result for query. Should be either 1 or 0.

if ($result != 1)

{

?>

<script>

alert ("That username or password doesn't exist");

</script>

<meta http-equiv="refresh" content = "1; URL = index.php">

<?php // Javascript alert saying that username or password was wrong then loading the page back to the main page.

}

else

{

$_SESSION['username'] = $username; // Setting the variable for the username so now you can use $_SESSION['username'] anywhere on your website to display who is logged in.

}

?>

You have to put session_start(); at the top of every webpage though. Now for the logout. Create a page called logout.php. You can link to this page however you'd like. All you need for this page is:

<?php

session_destroy(); //destroys the current session

<meta http-equiv="refresh" content = "1; URL = index.php"> //Reloads the page back to the index.php

?>

implode() is a handy little function that pieces together values of an array by putting a "glue" in between.

PRO:

fairly easy syntax

good management tool (phpmyadmin)

easy to integrate and use with PHP, Ruby etc.

very common therefore lots of tutorials and howtos

CONS:

performance

bad or missing RDMS features (like postgreSQL or other systems have)

limited capacities storage-wise

PHP++ is an object-oriented version of the PHP programming language. ++ is used in programming to increment a variable by one so it means an improved version of PHP.

Creating a webmail application in PHP involves using the related POP3 or IMAP libraries to connect to the mail system and cookies/sessions to save authentication information.

If you wish to check the syntax of your source code, you need to run the code through the PHP CLI with the -l option. There are also some online resources to validate the syntax. This will check only the syntax of your file. This will not however detect runtime errors or logic errors. You must absolutely run the script for the best possible code validation.

The function die() stops the script from running. See the example below:

<?php

die("this text will be outputted on the page");

echo "this text will not be shown due to the script ending when the die() function was called";

?>

To delay a script in seconds you would use the sleep() function as shown below:

<?php

echo "hello";

sleep(5); // delays the script for 5 seconds

echo "finished";

?>

use:

define("GREETING", "Hello you.", true);

1st parameter is the name for your constant

2nd parameter is the value of that constant

3rd parameter is whether or not you want the constant to be case-insensitive. Default is case sensitive.

http://php.net/manual/en/function.define.php

in programming, single quotes are for characters, and double quotes are for string, but in php, javascript, html, css i don't see any difference between the two.

It is fairly simple to check the length of a string in PHP. All you need to do is use the function strlen(). Below is an example of how it is used.

<?php

$my_text = "Hello";

echo strlen($my_text); // outputs 5

?>

$n = 10*(1+10)/2;

Please focus on the line number before the line of the error. There must be an array, with some issues with the index.

To merge arrays in PHP all you have to do is use the array_merge() function like shown below:

<?php

$array1 = array("Matt", "Michael", "Justin");

$array2 = array("Janice", "Janet", "Kylie");

$array3 = array_merge($array1, $array2);

?>

One thing to remember when merging arrays is you might be creating duplicate results, if you don't want 2 or more of the same result in the array remember to use the function array_unique() to remove the duplicate results from it!

When defining your function, do not put any arguments in the definition (e.g. function myFuntion()).

Inside the function, you can use func_num_args() and func_get_arg($number) to get the function's arguments.

Assuming you are using a User database and sessions, simply add a Session key. Auto generate this key as follows:

$newsession_key = SHA1( RAND(100000000,999999999));

Enter this in the database on the user row when logging in and store it in a session and in the database. Then on your code where you define the user logged in status you add something like:

$database_session = $DATABASE['sessionkey'];

If($database_session != $_SESSION['sessionkey']){

Unset($_SESSION['username'],$_SESSION['password'],$_SESSION['sessionkey']); #A*

}

A* Add in any sessions you use to keep the user logged in.

After you have uploaded it to your web host just go to the page in your browser and then you will see if it is working or not.

The $_POST array contains only variables supplied by a form that used the POST method, while the $_REQUEST array combines the $_POST, $_GET and $COOKIE arrays.

Xampp is made primarily to be used as a local server. It supports concurrent access to the best of my knowledge, however it will most likely be a slow solution. Access can be granted to multiple machines, however this will only work if the xampp server is active on the host machine. This poses many significant security risks.