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Using a for loop and range with array_reverse:

https://3v4l.org/7QMGl

<?php



$number = 25;

$columnCount = 4;



for($i = 1, $loopCounter = 1; $i <= $number; $i = $i + $columnCount, $loopCounter++) {

    $range = range($i, $i+$columnCount - 1);



    if($loopCounter % 2 === 0) {

        $range = array_reverse($range);

    }



    foreach($range as $n) {

        echo str_pad($n, 2, ' ', STR_PAD_LEFT) . " ";

    }



    echo "n";



}

We are increasing $i by the $columnCount on every iteration so we can always generate an array of the range of the numbers that have to be output in this row. That makes it very simple and clear if we have to reverse the numbers of the row.

str_pad helps us to maintain the correct spacing for e.g. single digits

Note: You might have to swap echo "n"; for echo "<br>"; if you are looking at the output in a browser.

Just to add a short version...

$columns = 4;

$rows = 3;

foreach ( array_chunk(range(1,$columns * $rows), $columns) as $row => $line )    {

    echo implode(" ", ($row % 2 == 0 )?$line:array_reverse($line) )."<br />";

}

The idea being to use range to create the numbers into an array and then use array_chunk to split it into lines. Then use implode() to output the lines - with the odd number lines reversed using array_reverse().

The following code will divide a range from 1 to 12 in chunks of 4. It will then walk through those chunks and print them forwards or backwards alternatively.

$forward = true;

array_walk(array_chunk(range(1, 12), 4), function ($a) use (&$forward) {

    echo $forward ? implode(' ', $a)  . '<br />' : implode(' ', array_reverse($a)) . '<br />';

    $forward = $forward ? false : true;

});

I decided to opt for the array_chunk method to create 'rows' which I then iterate over.

$max = 12; // The last number

$cols = 4; // The point at which a new line will start

$arr = array_chunk(range(1, $max), $cols); // Magic ;D



// Print the data.

foreach ($arr as $key => $row) {

    // This will reverse every other row

    $row = ($key % 2 === 0) ? $row : array_reverse($row);



    foreach ($row as $value) {

        $value = str_pad($value, strlen($max), ' ', STR_PAD_LEFT);

        echo "{$value} ";

    }

    echo "<br />";

}

I've given you some options too so that you can change the column lengths or the number of elements you want to produce.

The string padding won't be visible in your browser unless you wrap the output in <pre> tags because browsers only show one space at a time.

Code in action

$number = 12;

$elements_per_row = 4;

$left_to_right = true;

$processed_number_count = 0;

$result_array = ;

$temp = ;

for ($i=1; $i<=$number; $i++) {

    $temp = $i;

    $processed_number_count++;

    if ($processed_number_count === $elements_per_row) {

        $processed_number_count = 0;

        if ($left_to_right) {

            $result_array = $temp;

        } else {

            $result_array = array_reverse($temp);

        }

        $left_to_right = !$left_to_right;

        $temp = ;

    }

}



var_dump($result_array);

Then simply foreach $result_array to print desired pattern

This can be used variably for many other patterns which use same rule by modifying $number and $elements_per_row

Something like this.

bool forwardReverse = false;

int width = 4;

string line = "";

for (int i = 1; i < maxValue; i++)

{

    if (i % width == 0)

    {

        forwardReverse = !forwardReverse;

    Console.WriteLine(line);

    line = "";

    }



    if (forwardReverse)

    {

        line = line + i;        

    }

    else

    {

        line = i + line

    }

}

Every time you get to the end of a row (width) the Boolean flag changes and the order that new values are added is switched between appending and prepending.

Here is another simple solution just by extending the OP's method. You can try it out with different row and column sizes by changing values for first 2 variables.

<?

    $row_count = 3; //You can change this value depending to how many rows do you want to print

    $column_count = 4; //You can change this value depending to how many columns will be at each row



    $result = ''; //Variable to hold the output to print

    $num = 0; //Variable to hold temporary value for each element

    for ($i=1; $i<=$row_count; $i++) {

        //Every row

        for ($j=1; $j<=$column_count; $j++) {  

            //Every column

            if($i % 2 == 1) {

                //If row number is odd, increment the value starting from maximum element of previous row

                $num = (($i - 1) * $column_count) + $j;

            }

            else {

                //If row number is even, decrement the value starting from maximum element of current row

                $num = ($i * $column_count) - ($j - 1);

            }

            //Add calculated number to output with an extra space if it's only one character

            $result .= $num.($num < 9 ? '&nbsp; ' : ' '); 

        }  

        $result .= '</br>';  

    }

?>



<html>

    <head>

        <style type="text/css">

            body{

                font-family: Courier;

            }

        </style>

    </head>

    <body>

        <? echo $result; ?>

    </body>

</html>

Pretty much Nigel's answer, walk through a chunked range, echoing out each row, reversing every other:

<?php

$cols = 4;

$rows = 3;

array_walk(

    array_chunk(

        range(1, $rows*$cols),

        $cols

    ),

    function($v, $k) {

        if($k%2)

            $v = array_reverse($v);

        echo implode(' ', $v), "n";

    }

);

Output:

1 2 3 4

8 7 6 5

9 10 11 12

The following will do exactly what you want. Short yet effective.

for ($i = 4; $i <= 12; $i += 4) {

    echo (($i / 4) % 2) == 0 ? implode(' ', range($i, $i - 3)) . '<br />' : implode(' ', range($i - 3, $i)) . '<br />';

}