add_action( 'wp_head', 'so_enqueue_scripts' );
function so_enqueue_scripts(){
  wp_register_script( 'ajaxHandle', get_template_directory_uri() . '/myfile.php', array() );
  wp_enqueue_script( 'ajaxHandle' );
  wp_localize_script( 'ajaxHandle', 'myAjax', array( 'ajaxurl' => admin_url( 'admin_ajax.php' ) ) );
}

script:

jQuery('.mysubmitbuttin').click(function(){

      jQuery.ajax
      ({
          url: myAjax.ajaxurl,
          type: 'POST',
          data: {
            'action':'myaction',
            'value' : 'inc'
          },
          success: function(data)
          {
                alert(data);
          },
          error: function(data)
          {
                alert(data);
          }
      });
});

<?php

function so_wp_ajax_function()
{

    echo 'Imran';
    die('imran');
}
add_action( 'wp_ajax_myaction', 'so_wp_ajax_function' );
add_action( 'wp_ajax_nopriv_myaction', 'so_wp_ajax_function' );
?>