Question

What I’m trying to do is, to generate nav menu like

 <ul>
   <li>
     <ul>
...........
    </ul>
  </li>
 </ul>

from db, with one and only query. But onceI execute following function, it doesn’t stop. (Seems there is logic error). Please take a look, what’s wrong

<?php

function generateMenu($parent, $level, $menu, $utype) {
    global $db;

    $tree = array();
    $stmt = $db->prepare("select id, parent, name FROM navigation WHERE menu=? AND user_type=?") or die($db->error);
    $stmt->bind_param("ii", $menu, $utype) or die($stmt->error);
    $stmt->execute() or die($stmt->error);

    $stmt->store_result();
    $meta = $stmt->result_metadata();

// the following creates a bind_result string with an argument for each column in the query
// e.g. $stmt->bind_result($results["id"], $results["foo"], $results["bar"]);
    $bindResult = '$stmt->bind_result(';
    while ($columnName = $meta->fetch_field()) {
        $bindResult .= '$results["' . $columnName->name . '"],';
    }
    $bindResult = rtrim($bindResult, ',') . ');';

// executes the bind_result string
    eval($bindResult);
    $stmt->fetch();
    $stmt->close();
    while (list($id, $parent, $name) = $results) {
        $tree[$id] = array('name' => $name, 'children' => array(), 'parent' => $parent);
        if (!array_key_exists($tree[$parent]['children'][$id])) {
            $tree[$parent]['children'][$id] = $id;
        }
    }

    print_r($tree);
}

?>

Answer 1

Not sure if this is the issue, but I’d suggest using call_user_func_array instead of eval to call bind_result.

$bindResult = array();
while ($columnName = $meta->fetch_field()) {
   // Needs to passed by reference, so that it creates the $results array correctly
   $bindResult[] = &$results[$columnName->name];
}
call_user_func_array(array($stmt, 'bind_result'), $bindResult);

EDIT: Your issue is that $sql->fetch() needs to be called for each row, not just once. The code loops forever because you keep reading the same row. Try this:

function generateMenu($parent, $level, $menu, $utype) {
    global $db;

    $tree = array();
    $stmt = $db->prepare("select id, parent, name FROM navigation WHERE menu=? AND user_type=?") or die($db->error);
    $stmt->bind_param("ii", $menu, $utype) or die($stmt->error);
    $stmt->execute() or die($stmt->error);

    $stmt->store_result();
    $meta = $stmt->result_metadata();

    $bindResult = array();
    $results = array();
    while ($columnName = $meta->fetch_field()) {
       // Needs to passed by reference, so that it creates the $results array correctly
       $bindResult[] = &$results[$columnName->name];
    }
    call_user_func_array(array($stmt, 'bind_result'), $bindResult);

    while ($stmt->fetch()) {
        list($id, $parent, $name) = $results;
        $tree[$id] = array('name' => $name, 'children' => array(), 'parent' => $parent);
        if (!array_key_exists($tree[$parent]['children'][$id])) {
            $tree[$parent]['children'][$id] = $id;
        }
    }
    $stmt->close();

    print_r($tree);
}