PHP is a scripting language suitable for web backend development. It needs to run an environment that includes PHP interpreter, web server (such as Apache or Nginx) and database (such as MySQL). It is recommended to use integrated tools such as XAMPP, WAMP or MAMP to quickly configure it. 1. It is recommended to use PHP 8.0 and above for better performance and syntax support. 2. The PHP syntax is similar to C and Perl. The code is written in the <?php ... ?> tag, supporting variable definitions, conditional judgments, loop structures and function definitions. 3. The form data can be obtained through $\_GET and $\_POST. Upload the file with $\_FILES. Pay attention to verifying the input to prevent security vulnerabilities. 4. It is recommended to use PDO for database operations, which supports multiple databases and provides preprocessing functions to improve security. 5. When connecting to the database, DSN and error mode should be set, and the account password should be stored in the configuration file to restrict access permissions. Master these core points and quickly get started with PHP development.

PHP is a scripting language commonly used in back-end development, especially suitable for web development. It can be directly embedded in HTML, and output the results to the browser after execution through the server. If you are just starting to get involved in PHP, you may find the syntax simple but the purpose is vague. In fact, you can get started quickly by mastering several core concepts.

PHP's operating environment: first figure out how to run

To run PHP, you must first have a suitable environment. The most basic thing is to install a PHP interpreter, paired with a web server (such as Apache or Nginx), and a database (such as MySQL) to form the commonly known LAMP/WAMP/MAMP environment.

• If you are developing locally, you can use integrated toolkits such as XAMPP, WAMP or MAMP to get the environment configuration in one click
• For online deployment, most virtual hosts support PHP, and you can also use Linux Apache/Nginx PHP-FPM by using your own server.

One thing that is easy to ignore is the choice of PHP version. Different projects may rely on different versions. It is recommended to use version 8.0 or above for priority, which has better performance and more modern syntax.

PHP basic syntax: looks like a mixture of C and Perl

PHP syntax draws on many styles of C, Java and Perl. Variables start with $ and statements end with semicolons. When writing PHP code, it is usually between the <?php ... ?> tags.

Common structures include:

• Variable definition: $name = "John";
• Conditional judgment: if ($age > 18) { ... }
• Loop structure: for , foreach , while , etc.
• Function definition: function greet($name) { return "Hello, $name"; }

It is worth mentioning that PHP supports "short tags" = $name ?> , which is very convenient in templates, but some servers may turn off this function by default, so you need to pay attention to configuration.

Processing form and request data: the core link of web development

One of the most common uses of PHP is to process data submitted by HTML forms. When the user fills out the form on the web page and clicks to submit, the data will be sent to the server through GET or POST.

• GET data is obtained through the $_GET array, and POST is used as $_POST
• Use $_FILES to receive uploaded files. Remember to add enctype="multipart/form-data" to the form tag.
• All request parameters can be obtained through $_REQUEST , but it does not distinguish between sources and should be handled with care.

For example, if there is a username input box and the name attribute is username , you can get the value in PHP like this:

 $username = $_POST['username'];

But don't forget to filter and verify input, otherwise security vulnerabilities such as SQL injection or XSS attacks are prone to occur.

Using PHP to operate databases: Connections and queries are key

PHP provides a variety of ways to operate databases, the most commonly used are PDO (PHP Data Objects) and mysqli. PDO supports multiple database types and supports preprocessing statements, which is recommended as the preferred method.

The basic process for connecting to the database is as follows:

1. Set DSN (data source name)
2. Instantiate a PDO object
3. Set error mode for debugging
4. Perform a query or update operation

Sample code:

 $dsn = 'mysql:host=localhost;dbname=testdb';
$user = 'root';
$pass = '';

try {
    $pdo = new PDO($dsn, $user, $pass);
    $pdo->setAttribute(PDO::ATTR_ERRMODE, PDO::ERRMODE_EXCEPTION);

    $stmt = $pdo->query('SELECT * FROM users');
    while ($row = $stmt->fetch()) {
        echo $row[&#39;name&#39;] . &#39;<br>&#39;;
    }
} catch (PDOException $e) {
    echo &#39;Database connection failed: &#39; . $e->getMessage();
}

Be careful not to hard-code the database account password in the code, it is best to put it in the configuration file and restrict access.

Basically that's it. PHP is not difficult to learn, but to write safe and maintainable code, you still have to pay more attention to details, such as input verification, exception handling, database security, etc.

The above is the detailed content of The Fundamentals of PHP. For more information, please follow other related articles on the PHP Chinese website!