php - 当使用 PHP 和 MySQL 循环其余代码时，如何仅显示一段代码一次？

Question

我试图仅显示以下代码一次，而其余代码循环抛出。我的代码应该是什么样子以及应该放在哪里。截至目前，底部代码将不会显示，但如果我将其放入循环中，它将显示多次(不是我想要的)。

    //Display only once.
    if (!empty($row['category']) && !empty($row['url'])){
            echo '<h2>List of Links</h2>';
    }

这是完整的代码。

// Query member data from the database and ready it for display
$mysqli = new mysqli("localhost", "root", "", "sitename");
$dbc = mysqli_query($mysqli,"SELECT users.*, categories.*, users_categories.* FROM users_categories INNER JOIN users ON users_categories.user_id = users.user_id INNER JOIN categories ON users_categories.category_id = categories.id WHERE users_categories.user_id=3");

if (!$dbc) {
    // There was an error...do something about it here...
    print mysqli_error($mysqli);
}   
    //Display only once.
    if (!empty($row['category']) && !empty($row['url'])){
            echo '<h2>List of Links</h2>';
    }

$ctr = 0;
while ($row = mysqli_fetch_assoc($dbc)) {
    if (!empty($row['category']) && !empty($row['url'])) {
        if ($ctr%3 == 0) {
            echo '<div>';
        }
        $ctr ++;
        echo '<p"><a href="' . $row['url'] . '" title="' . $row['category'] . ' Category Link">' . $row['category'] . '</a></p>';
        if ($ctr%3 == 0) { 
            echo '</div>';
        }
    }

}
if ($ctr%3 != 0) { 
  echo '</div>';
}

Answer 1

也许您正在寻找:

if (mysql_num_rows($dbc) > 0){
    echo '<h2>List of Links</h2>';
}

通过将上面的代码替换为当前的 if 语句，标题将在查询返回行时显示，而不是在查询不返回任何内容时显示。

因此，完整的代码将是:

// Query member data from the database and ready it for display
$mysqli = new mysqli("localhost", "root", "", "sitename");
$dbc = mysqli_query($mysqli,"SELECT users.*, categories.*, users_categories.* FROM users_categories INNER JOIN users ON users_categories.user_id = users.user_id INNER JOIN categories ON users_categories.category_id = categories.id WHERE users_categories.user_id=3");

if (!$dbc) {
        // There was an error...do something about it here...
        print mysqli_error($mysqli);
}       
        //Display only once.
        if (mysql_num_rows($dbc) > 0){
            echo '<h2>List of Links</h2>';
        }

$ctr = 0;
while ($row = mysqli_fetch_assoc($dbc)) {
        if (!empty($row['category']) && !empty($row['url'])) {
                if ($ctr%3 == 0) {
                        echo '<div>';
                }
                $ctr ++;
                echo '<p"><a href="' . $row['url'] . '" title="' . $row['category'] . ' Category Link">' . $row['category'] . '</a></p>';
                if ($ctr%3 == 0) { 
                        echo '</div>';
                }
        }

}
if ($ctr%3 != 0) { 
  echo '</div>';
}