PHP MySQL Connect to a Database

Create a Connection to a MySQL Database

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

Example

In the following example we store the connection in a variable ($con) for later use in the script. The "die" part will be executed if the connection fails:

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Closing a Connection

The connection will be closed automatically when the script ends. To close the connection before, use the mysql_close() function:

PHP Forms

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 clicks on the submit button, the form data is sent to a PHP file, called "welcome.php":
"welcome.php" looks like this:

Output could be something like this:

 

 

 

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

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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

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

 

 

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):

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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 Syntax

Basic PHP Syntax

A PHP script always starts with <?php and ends with ?>. A PHP script can be placed anywhere in the document.
On servers with shorthand-support, you can start a PHP script with <? and end with ?>.
For maximum compatibility, we recommend that you use the standard form (<?php) rather than the shorthand form.

 

 

 

A PHP file must have a .php extension.
A PHP file normally contains HTML tags, and some PHP scripting code.
Below, we have an example of a simple PHP script that sends the text "Hello World" back 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".

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Comments in PHP

In PHP, we use // to make a one-line comment or /* and */ to make a comment block: