Php Superglobals Get Post Request Files Complete Guide

PHP Superglobals: GET, POST, REQUEST, FILES

Here’s a detailed explanation of the most commonly used PHP superglobals: $_GET, $_POST, $_REQUEST, and $_FILES.

1. $_GET

The $_GET superglobal is an associative array that stores data sent via the URL parameters (query string). Data passed via $_GET is visible to everyone (displayed in the URL) and has size limitations (usually around 2048 characters, depending on the browser and server settings).

Important Information:

• Used in URL-based data transmission.
• Accessible from http://example.com/page.php?var1=value1&var2=value2.
• Best for non-sensitive data since it's appended to the URL.
• Example:

  // URL: http://example.com/page.php?name=John&age=30
  echo $_GET['name']; // Outputs John
  echo $_GET['age'];  // Outputs 30
  

2. $_POST

The $_POST superglobal is another associative array that holds data sent from an HTML form using the method="post" attribute. Unlike $_GET, $_POST sends data securely (not visible in the URL) and can handle much larger amounts of data.

Important Information:

• Ideal for sensitive data like passwords.
• Does not appear in the URL.
• No size restrictions imposed by the URL length limit.
• Example:

  <form method="post" action="page.php">
    Name: <input type="text" name="name"><br>
    Email: <input type="email" name="email"><br>
    <input type="submit" value="Submit">
  </form>
  
  <?php
  if ($_SERVER["REQUEST_METHOD"] == "POST") {
    // Collect and sanitize input data
    $name = htmlspecialchars($_POST['name']);
    $email = htmlspecialchars($_POST['email']);
  }
  ?>
  

3. $_REQUEST

The $_REQUEST superglobal is also an associative array but combines the data from $_GET, $_POST, and $_COOKIE. It should be used with caution as it might introduce security risks if not properly handled.

Important Information:

• A combination of $_GET, $_POST, and $_COOKIE.
• Not recommended for secure data transmission due to potential security vulnerabilities.
• Can be less clear since data sources are combined.
• Example:

  // URL: http://example.com/page.php?name=John
  <form method="post" action="page.php">
    Name: <input type="text" name="name"><br>
    <input type="submit" value="Submit">
  </form>
  
  <?php
  echo $_REQUEST['name'];
  ?>
  

  In this example, if both a query parameter and a form field named name exist, $_REQUEST['name'] will return the value from the POST data (if available), otherwise, it will return the value from the URL.

4. $_FILES

The $_FILES superglobal is used when handling file uploads through a web form. It contains information about uploaded files, including their temporary locations on the server, names, types, and sizes.

Important Information:

• Contains file upload information.
• Used with enctype="multipart/form-data" in form tags.
• Provides various details such as name, type, size, tmp_name, and error.
• Requires proper validation to prevent security issues like file injection attacks.
• Example:

  <form action="upload.php" method="post" enctype="multipart/form-data">
    Select image to upload:
    <input type="file" name="myFile">
    <input type="submit" value="Upload Image" name="submit">
  </form>
  
  <?php
  if ($_SERVER["REQUEST_METHOD"] == "POST") {
    // Check if file was uploaded without errors
    if (isset($_FILES["myFile"]) && $_FILES["myFile"]["error"] == 0) {
      $allowed = ["jpg" => "image/jpg", "jpeg" => "image/jpeg", "gif" => "image/gif", "png" => "image/png"];
      $filename = $_FILES["myFile"]["name"];
      $filetype = $_FILES["myFile"]["type"];
      $filesize = $_FILES["myFile"]["size"];
  
      // Verify file extension
      $ext = pathinfo($filename, PATHINFO_EXTENSION);
      if (!array_key_exists($ext, $allowed)) die("Error: Please select a valid file format.");
  
      // Verify file size - 5MB maximum
      $maxsize = 5 * 1024 * 1024;
      if ($filesize > $maxsize) die("Error: File size is larger than the allowed limit.");
  
      // Verify MYME type of the file
      if (in_array($filetype, $allowed)) {
        // Check whether file exists before uploading it
        if (file_exists("upload/" . $filename)) {
          echo $filename . " is already exists.";
        } else {
          move_uploaded_file($_FILES["myFile"]["tmp_name"], "upload/" . $filename);
          echo "Your file was uploaded successfully.";
        } 
      } else {
        echo "Error: There was a problem uploading your file. Please try again."; 
      }
    } else {
      echo "Error: " . $_FILES["myFile"]["error"];
    }
  }
  ?>
  

Summary:

• $_GET: Data sent via URL parameters, visible and has size limitations. Suitable for non-sensitive data.
• $_POST: Securely send data from HTML forms, not visible in the URL. Better for larger data sets and sensitive information.
• $_REQUEST: Combines $_GET, $_POST, and $_COOKIE. Less secure and clear, should be avoided in security-critical applications.
• $_FILES: Handle file uploads from forms using enctype="multipart/form-data", providing necessary file details and ensuring safe processing.

Each of these superglobals plays an essential role in different scenarios within web development, and understanding when and how to appropriately use them is key to creating effective and secure PHP applications.

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