PHP LDAP simple JSON web service

<?php
$q = strtolower(preg_replace('/[^0-9a-zA-Z@\.]/i','',$_GET['q']));
$attribute = strtolower(preg_replace('/[^0-9a-zA-Z]/i','',$_GET['attribute']));

if (empty($q) || empty($attribute)){ echo "Missing parameter. Format should be index.php?q=XXXXXXX&attribute=YYYYYYY.\n\nq may be a NetID or email address.\nattribute may be any valid LDAP attribute (e.g., ndMail, telephoneNumber, or ndPrimaryAffiliation).\n\nAll values are case insensitive.\n\nSee eds.nd.edu for possible attributes and values."; die;}

$ds=ldap_connect("ldaps://ldap.nd.edu",636);  // must be a valid LDAP server!

if ($ds) {
    $r=ldap_bind($ds);     // this is an "anonymous" bind, typically
                           // read-only access

    if (strpos($q, '@')) {
        $filter = "ndmail=".$q;
    }
    else {
        $filter = "uid=".$q;
    }

    $sr=ldap_search($ds, "o=University of Notre Dame,st=Indiana,c=US", $filter);

    $info = ldap_get_entries($ds, $sr);

    echo "{\n   \"title\": \"LDAP\",\n      \"attributes\": {\n";

    for ($i=0; $i<$info["count"]; $i++) {
        echo "         \"netid\": \"" . $info[$i]["uid"][0] . "\",\n";
        echo "         \"".$attribute."\": \"" . $info[$i][$attribute][0] . "\"\n";
    }

    ldap_close($ds);
    echo "      }\n}";

} else {
    echo "{ \"Unable to connect to LDAP server\" }";
}
?>