- substr: documentation ( source)
- strpos: documentation ( source)
<?php
$r = '<div class="form-group>';
$r .= '<label class="control-label" for="id_f-variants-99999-is_active">Is active</label>';
$r = substr($r, 0, strpos($r, ">"));
$r .= '>';
$r .= '<label class="control-label" for="id_f-variants-99999-is_active">Is active</label>';
$r .= '<span class="unchecked">hoa</span>';
$r .= '<span class="checked">hoahoahoa</span>';
$r .= '</label>';
$r .= '</div>';