add_shortcode("mitsol_referral_contact_form", 'mitsol_referral_contact_form_replace_scode');    

function mitsol_referral_contact_form_replace_scode() {    

    $mrcf_html_content="";

    ob_start();

    mrcf_process_form();

    mrcf_html_form_code($mrcf_html_content);    

    /* Return the buffer contents into a variable */

    $msfb_html_content = ob_get_contents();

    /*Empty the buffer without displaying it. We don't want the previous html shown */

    ob_end_clean();

    /* The text returned will replace our shortcode matching text */

    return $msfb_html_content;

}

function mrcf_html_form_code($mrcf_html_content)

{            

    $mrcf_html_content.= '<form action="' . esc_url( $_SERVER['REQUEST_URI'] ) . '" method="post">

   <!-- put all form html elements here --> 

    <input type="submit" id="mrcf-submitted" name="mrcf-submitted" class="mrcf-input-boxes" value="Send"         </form></div>';    

    echo $mrcf_html_content;    

}

function mrcf_process_form() {

   //check if form submitted then process submitted form data  

    if ( isset( $_POST['mrcf-submitted'] ) ) { 

   // process submitted form data here 

   }

}

Even if you know wordpress as a beginner you can understand 

above codes, first i defined a short code, in the shortcode function 

i defined a function mrcf_html_form_code() which puts form htmls 

in web page. And when form submitted, mrcf_process_form() 

function checks if form submitted or not and processes form data.

 

Hope you liked it, i described everything in a very simple way. 

don't forget to share it.