创建一个乘法“网格”

Question

I am trying to create a simple multiplication grid in PHP

It should be of the format for example for a 2x2 grid:

0 1 2
1 1 2
2 2 4

My issue is getting it to start from 0.

This is my nested for loop so far:

 for($i=0;$i<=$_POST['rows'];$i++)
                {
                        echo "<tr>";
                        for($j=0;$j<=$_POST['columns'];$j++)
                        {
                                if($i==0)
                                {
                                        echo "<td>" . 1*$j . "</td>";
                                }
                                else
                                {
                                        $mult = $i * $j;
                                        echo "<td> $mult </td>";
                                }
                        }
                        echo "</tr>";
                }

But it gives the output:

0   1   2
0   1   2
0   2   4 

I need the column of 0's to be appropriate.

Answer 1

The way you're getting the top row of 0 1 2 3 is by that special-case on the X-axis. Do a similar special-case for the Y-axis ( $j ):

if ($i == 0) {
    ... 1 * $j ...
}
else if ($j == 0) {
    ... $i * 1 ...
}
else {
    ... $i * $j ...
}

Answer 2

You not only have $i==0 as special case but also $j==0 :

if($i==0)
{
    echo "<td>" . 1*$j . "</td>";
}
elseif($j==0)
{
    echo "<td>" . $i*1 . "</td>";
}
else
{
    $mult = $i * $j;
    echo "<td> $mult </td>";
}

Answer 3

I don't understand the way you construct your grid. All you need is a row indicator and the number for the multiplication not a nested loop. Second: Why don't you start with 1 instead of catching the case inside the loop. This would be my variant of the multiplication “grid”

<?php
    $rows = $_POST['rows'];
    $number = $_POST['columns'];

    for( $i=1; $i <= $rows; $i++) {
        $mult = $i * $number;
        echo "<tr>
                <td>" . $i.'*'. $j . "</td>
                <td>".$mult."</td>
            </tr>";
    }
?>

This would to a simple grid (x * y) = result. If you want a complete multiplication table it would be something like this:

<?php
    $rows = $_POST['rows'];
    $number = $_POST['columns'];
    echo "<tr><th></th>";
    for( $j=1; $j <= $number; $j++) {
         echo "<th>".$j."</th>";
    }
    echo "</tr>";
    for( $i=1; $i <= $rows; $i++) {
        echo "<tr>";
         echo "<th>".$i."</th>";
         for( $j=1; $j <= $number; $j++) {
                $mult = $i * $j;
                echo "<td>".$mult."</td>";
        }
        echo "</tr>";
    }
?>