PHP / MySQL - Nested List by recommendations / IDs - php

Question

We have on a social project a member database, which includes, which member recommended an other member. The fields of the database looks like this:
id | name | email | code | recruit_by
Now we want to print a nested list of the structure, who recommended whom on all deep levels.
We didn't get it running with the following code:
<?PHP
mysql_connect("www.mysqlserver.net", "database1", "password") or die(mysql_error());
mysql_select_db("project_db1") or die(mysql_error());
echo "<ul>";
$result = mysql_query("SELECT * FROM registration") or die(mysql_error());
while($row = mysql_fetch_array($result))
{
echo "<li class=\"level0\">" . $row['id'] . " - " . $row['name'] . " - " . $row['email'] . " - " . $row['recruit_by'] . "</li>";
// 1. Level
$result2 = mysql_query("SELECT * FROM registration WHERE recruit_by LIKE " . $row['id']) or die(mysql_error());
while($row2 = mysql_fetch_array($result2))
{
echo "<li class=\"level1\">1. " . $row2['id'] . " - " . $row2['name'] . " - " . $row2['email'] . " - " . $row2['recruit_by'] . "</li>";
// 2. Level
$result3 = mysql_query("SELECT * FROM registration WHERE recruit_by LIKE " . $row2['id']) or die(mysql_error());
while($row3 = mysql_fetch_array($result3))
{
echo "<li class=\"level2\">2. " . $row3['id'] . " - " . $row3['name'] . " - " . $row3['email'] . " - " . $row3['recruit_by'] . "</li>";
// 3. Level
$result4 = mysql_query("SELECT * FROM registration WHERE recruit_by LIKE " . $row3['id']) or die(mysql_error());
while($row4 = mysql_fetch_array($result4))
{
echo "<li class=\"level3\">3. " . $row4['id'] . " - " . $row4['name'] . " - " . $row4['email'] . " - " . $row4['recruit_by'] . "</li>";
// 4. Level
$result5 = mysql_query("SELECT * FROM registration WHERE recruit_by LIKE " . $row4['id']) or die(mysql_error());
while($row5 = mysql_fetch_array($result5))
{
echo "<li class=\"level4\">4. " . $row5['id'] . " - " . $row5['name'] . " - " . $row5['email'] . " - " . $row5['recruit_by'] . "</li>";
}
}
}
}
}
echo "</ul>";
?>

Answer 1

Very similar to an answer i gave here:
MySQL best practice: SELECT children recursive as performant as possible?
Again not the best use case for MySQL but yeah....
Dont do so many queries, do one
"SELECT * FROM registration"
Go through the result to build this as a tree like...
// use a database query to get this member info, here a simplified version
$member = array();
$member[] = array('id' =>'2', 'recruit_by' =>'1');
$member[] = array('id' =>'3', 'recruit_by' =>'2');
$member[] = array('id' =>'4', 'recruit_by' =>'3');
$member[] = array('id' =>'9', 'recruit_by' =>'1');
//use php to build a array containing all the recruit-relationships as a tree
function buildtree($member) {
$ref = array();
foreach($member as $mem){
$member_id = $mem['id'];
$parent = $mem['recruit_by'];
if(!is_array($ref[$member_id])) $ref[$member_id] = array('id' => $member_id);
if(!is_array($ref[$parent])) $ref[$parent] = array('id' => $parent);
$ref[$parent]['child'][] = &$ref[$member_id];
}
return $ref;
}
$tree = buildtree($member);
/// use a recursive function to output the tree
function echotree($tree, $parent = 0) {
foreach ($tree as $t) {
if($parent){
echo "$parent recruited " . $t['id'] . '<br>';
}
if(is_array($t['child']) && !$parent){
echotree($t['child'],$t['id']);
}
}
}
echotree($tree);
will give you:
2 recruited 3
1 recruited 2
1 recruited 9
3 recruited 4
should not be too hard to put this in whatever layout you wish.