为什么有几个foreach循环不能一起工作？

Question

I wrote this line to read three arrays and do some thing, but any thing does not running in these three foreaches!

foreach ($x_sort as $key => $x_name) {

    foreach ($y_sort as $key => $y_name){

        foreach ($z_sort as $key => $z_name){

            if ((!isset($y_name)) and (!isset($z_name)){
                echo $key . "." . $x_name . "," . "," . "<br>";

            }elseif ((isset($y_name)) and (!isset($z_name)){
                echo $key . "," . $x_name . "," . $key . ',' . $y_name . ',' . "<br>" ;
            }elseif ((!isset($y_name)) and (isset($z_name))){
                echo $key . "," . $x_name . ',' . ' ,' . $key . ',' . $z_name . "<br>" ;
            }elseif(isset($y_name)and isset($z_name))
            {
                echo $key . "," . $x_name . ',' . $key . ',' . $y_name . $key . ',' . $z_name . "<br>" ;
            }
        }
    }
}

Answer 1

There is a slight error in loop interpretation in your code.

For instance,

foreach ($x_sort as $key => $x_name) {

foreach ($y_sort as $key => $y_name){

Here both the for loops are unrelated. For a nested for loop to successfully iterate its elements, you must ensure that the value is being propagated from the top level loop.

So, your code will change to

foreach ($x_sort as $key => $x_name) {

foreach ($x_name as $key1 => $y_name){

Repeat the same procedure for the third loop.