require_once 'config.php';
require_once 'class.php';
$task = isset($_POST['task']) ? $_POST['task'] : '';
$ufrom = isset($_POST['ufrom']) ? (int) $_POST['ufrom'] : 72;
$uto = isset($_POST['uto']) ? (int) $_POST['uto'] : 117;
$db = new MySQLi(DB_HOST, DB_USER, DB_PASS, DB_NAME, 3306);
if ($db->connect_error) {
echo "Not connected, error: " . $db->connect_error;
} else {
switch ($task) {
case 'generate':
SixDegrees::prepareFriendList($db);
echo "<div style='color:green;'>Done!</div>";
break;
case 'build':
$result = SixDegrees::buildConnection($ufrom, $uto, $db);
if (!empty($result) && is_array($result) && is_array($result['path']) && count($result['path']) > 0) {
echo "<h3>Generated chain:</h3>";
include 'html/result.tpl.php';
echo "<h3>Ready to build some more?</h3>";
} elseif (!$result['brokenLink']) {
echo "<div style='color:red;'>Users are not connected</div>";
} else {
echo "<div style='color:red;'>Could not generate the chain</div>";
}
break;
default:
}
echo "<h3>Six Degrees of Separation Algorithm Demo</h3>";
include 'html/main.tpl.php';
}
/**
* Method to generate array of IDs of the users that are in a chain between the two given users $ufrom and $uto.
*
* @param MySQLi Database handler
* @param object Table record for user $ufrom
* @param object Table record for user $uto
* @param integer Radius of the minimum intersection circle we want to find
* @param array This is to be used internally only, should be left empty
* @param array This is to be used internally only, should be left empty
*
* @return null
*/
private function _findIntersection($db, $ufrom, $uto, $level, $from = array(), $to = array())
{
$t = "friends" . $level;
//name of a table field where list of friends of $level are kept
$from[$level] = explode(',', $ufrom->{$t});
$to[$level] = explode(',', $uto->{$t});
//the simplest case is when $ufrom and $uto are mutual friends
if ($level == 1 && (in_array($ufrom->id_user, $to[$level]) || in_array($uto->id_user, $from[$level]))) {
$this->_chainLength = 1;
return array($ufrom->id_user, $uto->id_user);
}
//see if $ufrom's circle of radius $level intersects with any of the circles of $uto of smaller or equal radius
for ($k = 1; $k <= $level; $k++) {
$intersection = array_intersect($from[$level], $to[$k]);
if (!empty($intersection) && is_array($intersection)) {
reset($intersection);
//set internal pointer to the first element of an array
$this->_chainLength = $k + $level;
//the length of the chain between $ufrom to $uto
//if there's an intersection with $level equal 1, then there's just one person in between $ufrom and $uto
if ($level == 1) {
return array($ufrom->id_user, current($intersection), $uto->id_user);
}
//$ufrom and $uto may have several people in common in the circle of the same radius
//So we just pick the first person in $intersection array
$result = $db->query("SELECT * FROM friends WHERE id_user = '******'");
$ucommon = $result->fetch_object();
//convert available friend levels of $ucommon to array
for ($i = 1; $i < self::_maximumCircleRadius + 1; $i++) {
$common[$i] = explode(',', $ucommon->{"friends" . $i});
}
$stack = array('to' => array(), 'from' => array());
SixDegrees::_reverseSearch($from, $common, $level, 1, $stack, 'from');
//build a chain from $ucommon to $ufrom
SixDegrees::_reverseSearch($to, $common, $k, 1, $stack, 'to');
//build a chain from $ucommon to $uto
//start: build the resulting array
$result = array($ufrom->id_user);
$j = count($stack['from']) - 1;
while ($j >= 0 && isset($stack['from'][$j])) {
//build a chain from $ufrom to $ucommon
$result[] = $stack['from'][$j];
$j--;
}
$result[] = current($intersection);
//add $ucommon himself to the chain
for ($j = 0; $j < count($stack['to']); $j++) {
//build a chain from $ucommon to $uto
$result[] = $stack['to'][$j];
}
$result[] = $uto->id_user;
//end: build the resulting array
return $result;
}
}
if ($level < self::_maximumCircleRadius) {
// we can continue until we reach _maximumCircleRadius
return $this->_findIntersection($db, $ufrom, $uto, $level + 1, $from, $to);
} else {
return null;
}
}
