The mystery of predefined arrays in PHP revealed

The mystery of predefined arrays in PHP is revealed

In PHP programming, arrays are a very common and powerful data structure that can be used to store multiple value. In addition to custom arrays, PHP also provides some predefined arrays, which can help us perform data operations more conveniently in different situations. This article will reveal some of the mysteries of predefined arrays in PHP and illustrate them with specific code examples.

1. $_SERVER array

$_SERVER is an array containing elements such as header information, path and script location. It is one of the most important predefined arrays in PHP. Through the $_SERVER array, we can obtain various useful information about the server environment, request information, etc.

// Get the path of the current PHP file
echo $_SERVER['PHP_SELF'];

// Get the server IP address
echo $_SERVER['SERVER_ADDR'];

// Get request method
echo $_SERVER['REQUEST_METHOD'];

2. $_GET array

$_GET is a predefined array used to collect data submitted by the form, passed in the URL through the GET method Parameters will be stored in the $_GET array. Through the $_GET array, we can easily get the parameter values ​​passed in the URL.

// Get the value of the parameter id in the URL
$id = $_GET['id'];
echo "The value of the parameter id is: " . $id;

3. $_POST array

$_POST is another predefined array used to collect data submitted by the form, similar to $_GET Compared with arrays, $_POST arrays are more secure because the data is sent through HTTP POST requests and will not be directly exposed in the URL.

// Get the username and password submitted in the form
$username = $_POST['username'];
$password = $_POST['password'];
echo "Username: " . $username . ", Password: " . $password;

4. $_SESSION array

$_SESSION is a predefined array used to store session data. Through session technology, we can maintain user login status and other information between different pages.

//Storage user login status
$_SESSION['user'] = 'John Doe';

// Get user login status
echo "Current user:" . $_SESSION['user'];

5. $_FILES array

$_FILES is a predefined array used to store file information when uploading files, through $ _FILES array, we can get relevant information about uploaded files, such as file name, file type, etc.

// Process file upload
if ($_FILES['file']['error'] === 0) {
    $file_name = $_FILES['file']['name'];
    $file_tmp = $_FILES['file']['tmp_name'];
    move_uploaded_file($file_tmp, "uploads/" . $file_name);
    echo "File uploaded successfully!";
} else {
    echo "File upload failed!";
}

Through the above introduction and examples of predefined arrays in PHP, we can see the application of these predefined arrays in different scenarios. Proficiency in these predefined arrays will help us perform data operations and development work more efficiently. I hope this article can help readers gain a deeper understanding of the mystery of predefined arrays in PHP.

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