How can PHP be used to populate an existing input field with the current date instead of creating a new one?

To populate an existing input field with the current date using PHP, you can use the `value` attribute in the HTML input tag and set it to `<?php echo date('Y-m-d'); ?>`. This will output the current date in the specified format inside the input field.

<input type="text" name="date" value="<?php echo date('Y-m-d'); ?>">