Roots.io searchform.php template hack to get search widget working in Polylang, only searching within the active language. 'soil-nice-search' disabled btw.

searchform.php

<?php

/*
 *
 * Roots.io searchform.php template hack to fix Polylang search
 *
 * Note: Polylang setting 'Hide URL language info for default language' should be enabled for this to work. 
 * Soil-nice-search disabled in Roots.
 *
 */

if(function_exists('pll_current_language')){

	$current_language = pll_current_language();
	$default_language = pll_default_language();

	if($current_language != $default_language){
		$language_subdir = $current_language.'/';
	} else {
		$language_subdir = '';
	}

}


?>
<form role="search" method="get" class="search-form form-inline" action="<?php echo esc_url(home_url('/'.$language_subdir)); ?>">
  <label class="sr-only"><?php _e('Search for:', 'roots'); ?></label>
  <div class="input-group">
    <input type="search" value="<?php echo get_search_query(); ?>" name="s" class="search-field form-control" placeholder="<?php _e('Search', 'roots'); ?> <?php bloginfo('name'); ?>">
    <span class="input-group-btn">
      <button type="submit" class="search-submit btn btn-default"><?php _e('Search', 'roots'); ?></button>
    </span>
  </div>
</form>

Just wanted to point out, your checking if a function exists (good) then setting a variable.

Then you use $language_subdir without checking if it exists, in the case of the function check failing this would be null and depending on your config throw an error.