如何在 foreach 循环（php）中按变量排序？

Question

在我的每个循环中，我想根据我的变量 $total resp 的值对我的选项进行排序。由data-total:

     <select>
                   <option data-total="0" value="" selected>--</option>
                   <?php 

                    $pdo = Database::connect();


                    $sql = "SELECT  *  FROM table_a;" ;

                    foreach ($pdo->query($sql) as $row) {

                            $a = $row['a'];
                            $number_a = $row['number_a'];               

                            $sql2 = "SELECT  *  FROM table_b WHERE a = '$a';" ;
                            $number_b = 0;

                            foreach ($pdo->query($sql2) as $row2) {
                                $number_b+= $row2['number']; 
                            }

                            $total = $number_a - $number_b;

                            echo '<option data-total="'.$total.'" value="'.$a.'">'.$a;

                    }

                    Database::disconnect();

                        ?>                                                          
     </select>

这可能吗？非常感谢！

Answer 1

在你的 for 循环中做这样的事情

$total_arr = array();
foreach ($pdo->query($sql) as $row) {

                            $a = $row['a'];
                            $number_a = $row['number_a'];               

                            $sql2 = "SELECT  *  FROM table_b WHERE a = '$a';" ;
                            $number_b = 0;

                            foreach ($pdo->query($sql2) as $row2) {
                                $number_b+= $row2['number']; 
                            }

                            $total = $number_a - $number_b;
                            $total_arr[$a] = $total;

                    }

arsort($total_arr);
foreach ($total_arr as $key => $val) {
    echo '<option data-total="'.$val.'" value="'.$key.'">'.$key;
}