How can I make this function work with recursion?

Question

Output:

3
3 4
3 4 5
3 4 5 6
3 4 5 6 7
3 4 5 6 7 8

function Triangle ($begin, $end) {
    if ($begin < 0 || $end < 0) {
        return;
    }
    if ($begin == $end) {
        return $a;
    }
    else {
        // non recursive
        for ($i = 1; $i <= $end; $i++) {
            for ($j = $begin; $j <= $i; $j++) {

                echo $j . " ";
            }
            echo "<br>";
        }
    }
}

This is what I made so far.

Answer 1

Here's one way:

function triangle ($begin, $end, $row = 1) {
    //stop when we've printed up to end
    if($end - $begin + 1 < $row) return;

    //let's start at the beginning :)
    for($i = 0; $i < $row; $i++){
        //the row number increments each time so we can keep adding.
        echo ($begin + $i)." ";
    }
    echo "<br>";
    //now recurse...
    triangle($begin, $end, $row + 1);
}

Usage:

triangle(3,9);

Output:

3 
3 4 
3 4 5 
3 4 5 6 
3 4 5 6 7 
3 4 5 6 7 8 
3 4 5 6 7 8 9

Answer 2

This should work for you:

(Here I just added the variable step which defines how many steps you make from $begin to $end and if $begin + $step == $end the function is done. If not It starts from $begin and makes X steps and as long as it doesn't reach the end I call the function again with a step more)

<?php

    function Triangle($begin, $end, $step = 0) {

        for($count = $begin; $count <= ($begin+$step); $count++)
            echo "$count ";
        echo "<br />";

        if(($begin + $step) == $end)
            return;
        else
            Triangle($begin, $end, ++$step);

    }

    Triangle(3, 8);

?>

output:

3 
3 4 
3 4 5 
3 4 5 6 
3 4 5 6 7 
3 4 5 6 7 8