WordPress disable search

functions.php

<?php

// Add to your functions.php file

function disable_search( $query, $error = true ) {
  if ( is_search() ) {
    $query->is_search = false;
    $query->query_vars[s] = false;
    $query->query[s] = false;
    // to error
    if ( $error == true )
    $query->is_404 = true;
  }
}

add_action( 'parse_query', 'disable_search' );
add_filter( 'get_search_form', create_function( '$a', "return null;" ) );