This note may be self-evident, but the functionality of ldap_sort threw off this sometime user of relational databases.

The following code will NOT do what you expect:

<?php

// omitted calls to connect and and bind to LDAP server...

// attributes we want to retrieve from LDAP server
$ldap_attributes = array ( 'cn', 'o', 'mail' ) ;

// retrieve attributes from matching entries
$search_results = ldap_search ( $ldap_conn, 'dc=example,dc=org', '(objectclass=*)', 0, 500, 30 ) ;

// sort entries by last name ('sn')
ldap_sort ( $ldap_conn, $search_results, 'sn' ) ;

?>

The entries will NOT be sorted by last name. Why not? Because LDAP doesn't function like a RDBMS; you cannot sort a result set on an arbitrary field, regardless of whether you "selected" it. You must always include the attribute by which you want to sort your entries among the requested attributes (add 'sn' to $ldap_attributes, in this case).

Hope this is helpful to some other folks who scratched their heads when they tried to sort entries and it didn't work out...

I wondered how to sort after a dn, for just show a tree view. I tried to set $sortfilter = 'dn', but that didn't work. Than I tried with a blank string ''. That worked, the entries are sorted by dn.

If you are wanting to sort by multiple attributes, for instance ordering by last name and then first name,  try this function. This is similar to "ORDER BY lastname, firstname"  in SQL.

This function uses an insertion sort algorithm, which is somewhat faster then the old-fashoned bubble sort.  The second argument is an array containing the attributes you want to sort by. (this functon won't do descending or ascending..  feel free to add it!)

<?php
/**
 * @param array $entries
 * @param array $attribs
 * @desc Sort LDAP result entries by multiple attributes.
*/
function ldap_multi_sort(&$entries, $attribs){
    for ($i=1; $i<$entries['count']; $i++){
        $index = $entries[$i];
        $j=$i;
        do {
            //create comparison variables from attributes:
            $a = $b = null;
            foreach($attribs as $attrib){
                $a .= $entries[$j-1][$attrib][0];
                $b .= $index[$attrib][0];
            }
            // do the comparison
            if ($a > $b){
                $is_greater = true;
                $entries[$j] = $entries[$j-1];
                $j = $j-1;
            }else{
                $is_greater = false;
            }
        } while ($j>0 && $is_greater);
        
        $entries[$j] = $index;
    }
    return $entries;
}
?>

Here's a simple LDAP sort function I wrote:

<?php
function sort_ldap_entries($e, $fld, $order)
{
    for ($i = 0; $i < $e['count']; $i++) {
        for ($j = $i; $j < $e['count']; $j++) {
            $d = strcasecmp($e[$i][$fld][0], $e[$j][$fld][0]);
            switch ($order) {
            case 'A':
                if ($d > 0)
                    swap($e, $i, $j);
                break;
            case 'D':
                if ($d < 0)
                    swap($e, $i, $j);
                break;
            }
        }
    }
    return ($e);
}

function swap(&$ary, $i, $j)
{
    $temp = $ary[$i];
    $ary[$i] = $ary[$j];
    $ary[$j] = $temp;
}
?>

so that it can be invoked like:

<?php
    $entries = sort_ldap_entries($entries, 'mail', 'A'); // sort entries by ascending order of mail
?>

where,
    `$entries' is the array returned by ldap_get_entries() function.

This might be useful to those who still run older versions of PHP (<= 4.2.0) on their web servers :-)

This function applies strcmp() to each attribute (given by sortfilter) in order to sort the entries returned by the server.  To order search results ascending by last name, try passing "sn" as the sortfilter argument.  This function does not play nice with multi-valued attributes.

Something real simple i wrote to sort directory searches by a persons last name.

<?php
for($i=0;$i<$result["count"];$i++)
{

$lastname = $result[$i]["sn"][0];

$lnames["$i"]=$lastname;

}//for i

@asort($lnames);
?>