如何在Drupal 7中创建自定义块？

I want to create a custom block in which I want to show custom form.

Form will contain only two element.

• input box (#centimeter)
• submit button

When this submit button is clicked I want to convert this centimeter in inch and display the result below this form and I want to show this in block in sidebar.

My questions:

1. How to do this?
2. I tried following link but don't know where to write the code - should I create any php file in some folder?
3. What to do if I want to show this block as a page with some url like /measurement/convert-cm-to-inches

http://kahthong.com/2013/06/create-your-own-custom-drupal-block-programmatically

Hope this may help you.

<?php
/**
 * Implements hook_block_view().
 */
function your_module_block_view($block_name = '')
{
    // in my example I show the form only in the front page.
    // You can show it where you want, obviously
    if (!drupal_is_front_page())
    {
        return NULL;
    }

    $form = drupal_get_form('your_module_form');
    $block = array
    (
        // 'subject' => t('Subject'),
        'content' => $form,
    );

    return $block;
}

/**
 * Implements hook_form().
 */
function your_module_form($form, &$form_state)
{
    // now I add a text field to the form
    // with a label and fixed dimensions (you never know...)
    $form['text'] = array
    (
      '#title' => t('Label for the text box'),
      '#type' => 'textfield',
      '#size' => 32,
      '#maxlength' => 128,
    );

    // now I add also a button
    $form['submit'] = array
    (
       '#type' => 'submit',
       '#value' => t('Submit'),
    );

    // and now I assign a my function as handler of the submit event 
    $form['#submit'][] = 'your_module_submit_handler';
    return $form;
}

function your_module_submit_handler($form, &$form_state)
{
    // this function will be executed after the click
    // event of the user on the "submit" button.
    // here I only print a message
    // you can access a database, redirect, or whatever you want, obviously 
    drupal_set_message(t('Ok!'));
}
?>