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antoine dot php dot net at bonnefoy dot eu ¶
9 years ago
Hello,

Little corrections to nemanja  post. 
- There was a warning if connection is denied by firewall (adding @ before fsockopen)
- fclose parameter was incorrect. 

With this approach, you get a real nice failover functionality, take for an example a company with a dozen of DC-a distributed along distant places, this way your PHP program will always have high availability if at least one DC is active at present.
<?php
function serviceping($_host, $_port = 389, $_timeout = 1) {
    $op = @fsockopen($_host, $_port, $errno, $errstr, $_timeout);
    if (!$op) {
        echo "KO!";
        return 0;
        
    } //DC is N/A
    else {
        fclose($op); //explicitly close open socket connection
        return 1; //DC is up & running, we can safely connect with ldap_connect
    }
}

function ldap_connect_failover($_domain) {
// ##### STATIC DC LIST, if your DNS round robin is not setup
//$dclist = array('10.111.222.111', '10.111.222.100', '10.111.222.200');
// ##### DYNAMIC DC LIST, reverse DNS lookup sorted by round-robin result
    $dclist = gethostbynamel($_domain);

    foreach ($dclist as $dc) {
        if (serviceping($dc) == true) {
            break;
        } else {
            $dc = 0;
        }
    }
//after this loop, either there will be at least one DC which is available at present, or $dc would return bool false while the next line stops program from further execution

    if (!$dc) {
        return false;
    } //user being notified

    return ldap_connect($dc);
}
?>
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