<?php
$str = '<span class="text">Lastly, <b>set up an Administrator Account</b> by entering the requested fields. If you wish to use Active Directory, enter the information of an Active Directory user.</span>';
$replace_o_matic = array(
'/<b>/' => '',
'/<\/b>/' => '',
);
printf (preg_replace(
array_keys($replace_o_matic),
array_values($replace_o_matic),
$str,
1)
);
<span class="text">Lastly, set up an Administrator Account by entering the requested fields. If you wish to use Active Directory, enter the information of an Active Directory user.</span>