<?php
wp_enqueue_script(‘jquery-ui-datepicker’);
wp_enqueue_style(‘jquery-style’, ‘http://ajax.googleapis.com/ajax/libs/jqueryui/1.8.2/themes/smoothness/jquery-ui.css’);
?>

<input type=”text” id=”MyDate” name=”MyDate” value=””/>

<script type=”text/javascript”>

jQuery(document).ready(function() {
jQuery(‘#MyDate’).datepicker({
dateFormat : ‘dd-mm-yy’
});
});

</script>

<?php 
class plugin
{

	function pulgin()

	{

		----------------

		add_filter('plugin_action_links_' . plugin_basename(__FILE__), array(&$this, 'filter_plugin_actions'), 10, 2 );

	}

	function filter_plugin_actions($links, $file) {
		$settings_link = '<a href="admin.php?page=master-page-dashboard">' . __('Settings', $this->localizationDomain) . '</a>';
		array_unshift($links, $settings_link); // before other links

		return $links;
	}
}
?>

<?php print_r(get_intermediate_image_sizes()); ?>

o/p
Array ( [0] => thumbnail [1] => medium [2] => large [3] => post-thumbnail [4] => large-feature [5] => small-feature )

<?php
/**
* Custom admin login Logo
*/
function custom_login_logo() {
     echo '<style type="text/css">                                                                   
         h1 a { background-image:url('.get_stylesheet_directory_uri().'/images/login.png) !important; 
         height: 120px !important; width: 410px !important; margin-left: -40px;}                            
     </style>';
}

add_action('login_head', 'custom_login_logo');

--------------------------------------------
/**
* Custom admin login header link
*/
function custom_login_url() {
	return home_url( '/' );
}
add_filter( 'login_headerurl', 'custom_login_url' );

--------------------------------------------

/**
* Custom admin login header link alt text
*/
function custom_login_title() {
	return get_option( 'blogname' );
}
add_filter( 'login_headertitle', 'custom_login_title' );
?>

PHP

function myFunction(){
	//do something

	//echo json_encode(array); // if required json result
	die();
}
add_action('wp_ajax_myFunction', 'myFunction');
add_action('wp_ajax_nopriv_myFunction', 'myFunction');

-------------------------------------------------------------------

Jquery

jQuery(document).ready(function($) {

	 $.ajax({
	 	url: ajaxurl,
		data: {
	 			'action':'myFunction',
	 			'data1' : 'value1',
	 			'data2' : 'value2'

	 	},

		// dataType: 'JSON', // if required json result

	 	success:function(data) {
	 		//var obj = jQuery.parseJSON(data); // converting string to json object
	 		console.log(data);
	 	},

	 	error: function(errorThrown){

			 console.log(errorThrown);
	 	}

	 }); 

});

http://wptheming.com/2013/07/simple-ajax-example/

http://codex.wordpress.org/AJAX_in_Plugins

/* = WordPress Core
————————————————————– */
.alignnone {
margin: 5px 20px 20px 0;
}

.aligncenter,
div.aligncenter {
display: block;
margin: 5px auto 5px auto;
}

.alignright {
float:right;
margin: 5px 0 20px 20px;
}

.alignleft {
float: left;
margin: 5px 20px 20px 0;
}

.aligncenter {
display: block;
margin: 5px auto 5px auto;
}

a img.alignright {
float: right;
margin: 5px 0 20px 20px;
}

a img.alignnone {
margin: 5px 20px 20px 0;
}

a img.alignleft {
float: left;
margin: 5px 20px 20px 0;
}

a img.aligncenter {
display: block;
margin-left: auto;
margin-right: auto
}

.wp-caption {
background: #fff;
border: 1px solid #f0f0f0;
max-width: 96%; /* Image does not overflow the content area */
padding: 5px 3px 10px;
text-align: center;
}

.wp-caption.alignnone {
margin: 5px 20px 20px 0;
}

.wp-caption.alignleft {
margin: 5px 20px 20px 0;
}

.wp-caption.alignright {
margin: 5px 0 20px 20px;
}

.wp-caption img {
border: 0 none;
height: auto;
margin: 0;
max-width: 98.5%;
padding: 0;
width: auto;
}

.wp-caption p.wp-caption-text {
font-size: 11px;
line-height: 17px;
margin: 0;
padding: 0 4px 5px;
}

/*==============*/