Part of a file from http://webcodingeasy.com/PHP-Security/Managing-X509-certificates-using-PHP

create_identity_cer.php

<?php
// Returns a cer encoded SSL certificate
function create_identity_cer( 
    $countryName,  $stateOrProvinceName, $localityName, $organizationName, 
    $organizationalUnitName, $commonName, $emailAddress, $foafLocation)
{
    // Create the DN array for the openssl function calls
    $fields = array(
        'countryName', 
        'stateOrProvinceName', 
        'localityName', 
        'organizationName', 
        'organizationalUnitName', 
        'commonName', 
        'emailAddress',
    );
    
    $dn = array();
    foreach ($fields as $f)
    {
        if (${$f})
            $dn[$f] = ${$f};
    }

    // if the $dn array is NULL at this point set country name to the default of GB
    if (empty($dn))
        $dn = array("countryName" => "GB");