function get_checkbox($name, $value, $checked, $tags = array())
{
    $checked_str = $checked ? ' checked' : '';
    $html = '<input  class="form-control" type="checkbox" name="' . $name . '" value="' . htmlspecialchars($value) . '"' . $checked_str . get_tags_string($tags) . '>';
    return $html;
}
<?php

function get_tags_string($tags_array)
{
    $str = "";
    foreach ($tags_array as $tag) {
        $str .= 'tag_' . $tag->slug . ' ';
    }
    return $str;
}
get_header('estandar');
?>
<ul id="filters" class="clearfix">
	<?php 
$tags_array = get_tags();
$tag_str = get_tags_string($tags_array);
?>
 
	<li><span class="filter active" data-filter="<?php 
echo $tag_str;
?>
">All</span></li>
	<?php 
foreach ($tags_array as $tag) {
    ?>
	<li><span class="filter" data-filter="tag_<?php 
    echo $tag->slug;
    ?>
"><?php 
    echo $tag->name;
    ?>