在PHP foreach循环中对项目进行分组[关闭]

Question

I want somehow to group items in foreach loop so i can display them effectively. For example if I have the following MySql table:

user_id username group_id
1       John     1
2       Mark     2
3       Steve    2

I want the users in the group_id 2 to be shown together in <div class="group2">Username 1: Mark, Username 2: Steve</div> and users in group_id 1 <div class="group1">Username John</div>

I hope you will understand the question.

Answer 1

You can do this fairly easily by ordering your query by group_id and then keeping track of when it changes. Something like this:

$query = "SELECT * FROM table ORDER BY group_id";
$results = $mysqli->query($query);
$lastGroup = 0;
while ( $row = $results->fetch_assoc() )
{
    if ( $row['group_id'] != $lastGroup )
    {
        // If there is already a div open we need to close it, so if 
        // last group > 0 then a div has been opened.
        echo ($lastGroup > 0 ? '</div>' : '') . '<div class="group' . $row['group_id'] . '">';
    }
    $lastGroup = $row['group_id'];
    echo $row['username'] . '<br>';
}
// close the last open div
echo '</div>';

Alternatively you can use the MySQL GROUP_CONCAT function to get back all the usernames in a group. Use this:

$query = "SELECT group_id,
GROUP_CONCAT(username) as users
FROM table
GROUP BY group_id";

$results = $mysqli->query($query);
while ( $row = $results->fetch_assoc() )
{
    echo '<div class="group' . $row['group_id'] . '">' . $row['users'] . '</div>';
}