$re = '/<td bgcolor="#EEEEEE" align="center"><input id="([-0-9a-zA-Z =~:#\"%>\/<]*) /m';
$str = '<td bgcolor="#EEEEEE" align="center"><input id="selectedUser12" type="checkbox" name="selectedUser" disabled value="sid759e0649e819999a3dc12a93ad2af5204a83f20600000000:cshah2op~~Admin%20Users" ></td>
<td bgcolor="#EEEEEE"> </td>
<td bgcolor="#EEEEEE">cshah2op </td>';
$subst = "$1 $2";
$result = preg_replace($re, $subst, $str);
echo "The result of the substitution is ".$result;
Please keep in mind that these code samples are automatically generated and are not guaranteed to work. If you find any syntax errors, feel free to submit a bug report. For a full regex reference for PHP, please visit: http://php.net/manual/en/ref.pcre.php