How to Create Sharing Buttons similar to Jetpack | http://www.ibenic.com/create-sharing-buttons-similar-jetpack/

content.php

<?php

function my_share_render_in_content( $content ) {
	ob_start();
	?>
		<ul id="my_share" class="my_share">
			<li> 
				<a href="<?php the_permalink();?>?my_share=facebook">Facebook</a>
			</li>
			<li> 
				<a href="<?php the_permalink();?>?my_share=twitter">Twitter</a>
			</li>
		</ul>
	<?php
	$content .= ob_get_contents();
	ob_end_clean();
	return $content;
}

add_action( 'the_content', 'my_share_render_in_content');

facebook_share.php

<?php

class WordPressShare_Facebook extends WordPressShare {

	public $share_url = 'https://www.facebook.com/sharer/sharer.php';

	public function get_link() {
		$url = $this->share_url . '?u=' . $this->get_url() . '&t=' . $this->get_text();
		return $url;
	}
}

my_share_social.php

<?php

function my_share_social( $social ) {
	
  $social_media = array(
  	'facebook' => 'WordPressShare_Facebook',
  	'twitter' => 'WordPressShare_Twitter' );
  
  if( isset( $social_media[ $social ] ) ) {
  	$social_media_class = $social_media[ $social ];
  
  	$social_object = new $social_media_class();
  	$social_object->share();
  }

}

script.js

(function($) {
	$( document ).ready( function(){
		$("#my_share a").on('click', function(e){
			e.preventDefault();
			var href = $( this ).attr("href");

			window.open( href, 'Share', 'width=600, height=400');
		})
	});
})(jQuery);

share_redirect.php

<?php

function my_share_redirect() {
	 if( isset( $_GET['my_share'] ) ){
	 	my_share_social( $_GET['my_share'] );
	 }
}

add_action( 'template_redirect', 'my_share_redirect' );

style.css

.my_share {
	padding:0;
	margin:0;
	list-style: none;
	display: block;
	width:100%;
}
.my_share:after {
	display: table;
	content: '';
	clear: both;
}

.my_share li {
	float: left;
}
.my_share a {
	padding: 0.5em .75em;
	background-color:white;
	color: black;
	border: 1px solid gray;
	box-shadow: 0px 1px 1px #ccc;
}

.my_share a:hover,
.my_share a:focus {
	background-color:black;
	color:white;
}

twitter_share.php

<?php

class WordPressShare_Twitter extends WordPressShare {

	public $share_url = 'https://twitter.com/intent/tweet';

	public function get_link() {
		$url = $this->share_url . '?url=' . $this->get_url() . '&text=' . $this->get_text();
		return $url;
	}
}

wordpress_share.php

<?php

abstract class WordPressShare {

	/**
	 * Text to be shared
	 * @var string
	 */
	public $text = '';

	/**
	 * URL to be shared
	 * @var string
	 */
	public $url = '';

	/**
	 * Social Media URL that is used for sharing
	 * @var string
	 */
	public $share_url = '';

	/**
	 * Post Object
	 * @var mixed
	 */
	public $post = null;

	/**
	 * Asign the object and meta data
	 */
	public function __construct() {
		$this->post = get_post( get_the_id() );

		if( $this->post ){
			$this->get_meta();
		}
	}
	
	// ...
}

wordpress_share2.php

<?php

abstract class WordPressShare {

	//...
	
	/**
	 * Assigning the meta from the Post Object
	 * @return void
	 */
	protected function get_meta() {
		$this->text = $this->post->post_title;
		$this->url = get_permalink( $this->post );
	}
	
}

wordpress_share3.php

<?php

abstract class WordPressShare {

	//...
	
	/**
	 * Get the URL
	 * @return string 
	 */
	protected function get_url(){
		return $this->url;
	}

	/**
	 * Get the URL encoded text
	 * @return string 
	 */
	protected function get_text() {
		return urlencode( $this->text );
	}

	/**
	 * Get the link to which we will redirect our visitor
	 * @return string
	 */
	public function get_link() {

	}

	/**
	 * Redirect the visitor to the sharing link
	 * @return void 
	 */
	public function share() {

		$link = $this->get_link();

		if( $link ){
			wp_redirect( $link );
			exit;	
		}
		
	}
	
}