The core purpose of PHP is to create websites and online applications. This is how it is most commonly used. Web applications become dynamic with PHP, which enables user interaction.
Introduction to PHP In Web Application
PHP is used to build web apps. PHP code in HTML pages runs when viewed. The web server interprets this PHP code, producing HTML or other output that the user sees. The end product is an interactive webpage. PHP was created mainly for the web, to be used as a template language embedded in HTML files. Although PHP and HTML are frequently used together when developing web applications, PHP does not need to be embedded; a PHP file can be created without HTML.
Dynamic Content Generation
The creation of dynamic content is made possible by the ability to embed code and have it run on the server. The PHP code can provide dynamic output depending on a number of variables, including user input, database data, and the current date and time, rather than presenting a static HTML file that is always the same. The online application becomes interactive as a result.
For instance, PHP can be used to create HTML, XML, PDF, and graphical documents as well as to communicate with databases to show dynamic data.
Using the date() method to display the current date is a straightforward example of dynamic content generation:
<?php
// Using the date() function to output the current date dynamically
echo "Today's date is: " . date("Y-m-d");
?>When the page is queried, this piece of code, which is embedded within an HTML file (usually saved with a.php extension), would output the current date.
HTML Forms Refresher and Getting Information from the User
HTML forms are a common way for users to input data to online apps. Text input fields, checkboxes, radio buttons, and submit buttons allow users to enter or select data. HTML forms are recommended for PHP online applications.
These forms are especially well-suited for PHP. Using HTML forms, the online application gathers and processes user information.
HTML Form Actions & Methods (GET and POST)
The file to which the completed form data is posted using the action property is specified by an HTML tag. Additionally, it identifies the protocol usually GET or POST that is used to transmit the data to the server.
- The GET method appends form data to URL query parameters. Although there are limits on the amount of data transferred and the data is exposed in the URL, this is suitable for data retrieval or submitting a form without sensitive information.
- The form data is sent via the POST method in the HTTP request’s body. This is typically utilised for activities that alter data on the server (such as adding or altering records) and for submitting huge volumes of data or sensitive information (such as passwords).
PHP makes the data from every form element available to the PHP script (the file indicated in the action property) when a form is submitted to it.
Accessing Form Variables in PHP ($_GET, $_POST)
PHP has built-in features that make it simple to access data entered into forms. The $_POST superglobal array contains the data that was sent using the POST method. The $_GET superglobal array holds GET-submitted data. These associative arrays use user-submitted form element data as values and form element name attributes as keys.
Processing input with a PHP script and a simple HTML form:
First, the HTML form (index.html):
<!DOCTYPE html>
<html>
<head>
<title>Simple Form</title>
</head>
<body>
<h2>Enter Your Name</h2>
<!-- The form sends data to process_form.php using the POST method -->
<form method="post" action="process_form.php">
Name: <input type="text" name="userName">
<br><br>
<input type="submit" value="Submit">
</form>
</body>
</html>
Next, the PHP script to process the form data (process_form.php):
<!DOCTYPE html>
<html>
<head>
<title>Form Result</title>
</head>
<body>
<h2>Form Submission Result</h2>
<?php
// Check if the form was submitted using POST
if ($_SERVER["REQUEST_METHOD"] == "POST") { // [48] check method
// Check if the 'userName' field exists in the $_POST array
if (isset($_POST['userName'])) { // [56] using isset()
// Access the submitted data
$name = $_POST['userName']; // [48] accessing $_POST
// Display a dynamic greeting
echo "<p>Hello, " . htmlspecialchars($name) . "!</p>"; // [44] string concatenation, htmlspecialchars for safety
} else {
echo "<p>Name field was not submitted.</p>";
}
} else {
echo "<p>This page should be accessed via a form submission.</p>";
}
?>
</body>
</html>After the user submits index.html’s form, the browser sends data to process_form.php via POST. Process_form.php checks if the request type is POST, retrieves the userName input field data from $_POST[‘userName’], then creates a dynamic greeting using this name.
This illustrates how PHP easily combines with HTML forms to produce dynamic web apps that are able to gather and respond to user input.