LDAP - 从DN中提取CN值

I want to extract the CN value from DNs returned by $output[$i] in the code below:

$result=ldap_search($conn, $ldap_dn, "cn=$myId",array("givenname","sn","memberof","primarygroupid")) or die("No search data found."); 

$info = ldap_get_entries($conn, $result);

$output = $info[0]['memberof'];
array_shift($output);

$arrlen = count($output);
       for ($i=0; $i<$arrlen; $i++)
          {
          print $output[$i] . "
";
          }

Example output is

CN=FMDHS-PLM-WebTest-3,OU=Permission,OU=Groups,DC=uniwa,DC=uwa,DC=edu,DC=au

So in this example I want to just get FMDHS-PLM-WebTest-3

Any ideas how I can do this? Do I need to parse the string with PHP or is there something I can use in LDAP to acheive this?

EDIT

I ended up using ldap_explode_dn

$arrlen = count($output);
       for ($i=0; $i<$arrlen; $i++)
          {  
        $parsr=ldap_explode_dn($output[$i], 0); 
        print str_replace('CN=', '', $parsr[0]) . "
";
          }

I made this sample test:

<?php
$sample = "CN=FMDHS-PLM-WebTest-3,OU=Permission,OU=Groups,DC=uniwa,DC=uwa,DC=edu,DC=au";
$test = explode(",",$sample);
echo $test[0];
?>