What is the significance of using enctype="multipart/form-data" in PHP file uploads?

When uploading files in PHP, using enctype="multipart/form-data" in the form tag is necessary to ensure that the file data is properly encoded and sent to the server. This enctype allows files to be included in the request body, which is required for handling file uploads in PHP. Without specifying this enctype, the file data will not be correctly processed by the server.

<form action="upload.php" method="post" enctype="multipart/form-data">
    <input type="file" name="file">
    <input type="submit" value="Upload">
</form>