Lattice Multiplication Algorithm to Multiply Extremely Large Numbers in the Browser

lattice_multiplication.php

<?php
// NOT COMPLETE YET!
//<li>Store number1 and number2 as variables (num1, num2)</li>
echo '<p>Store number1 and number2 as variables: <br>';
$numX = $_POST["numX"];
$numY = $_POST["numY"];
echo $numX . '<br>' . $numY . '</p>';

//    <li>num1 and num2 toArray</li>
echo '<p>Number 1 and number 2 as array: <br>';
$arrX = str_split($numX, 1);
$arrY = str_split($numY);
var_dump($arrX);
echo '<br>';
var_dump($arrY);
echo '</p>';

//    <li>Variables to count the number of characters in each number (cnt, cnt2)</li>
echo '<p>Variables to count the number of characters in each number (cnt, cnt2): <br>';
$cntX = count($arrX);
$cntY = count($arrY);
echo $cntX . '<br>' . $cntY . '</p>';

//    <li>Array variable to store results of lattice (lattice[]) equation</li>
echo  '<p>Array variable to store results of lattice (lattice[]) equation</p>';
$lattice = array();

//    <li>Array variable to store 2 digits or more. (2plus[])</li>
echo '<p>Array variable to store 2 digits or more. (plus[])</p>';
$plus = array();

//    <li>If cnt1 < cnt2 then counter = cnt2 else counter = cnt1</li>
echo '<p>If cnt1 < cnt2 then counter = cnt2 else counter = cnt1 <br>';

$counter = 0;

function greater($a, $b){
    if($a > $b){
        $counter = $a;
    }
    else{$counter = $b;}
    echo $counter . '</p>';
    return $counter;
}
greater($cntX, $cntY);



echo 'multiply<br>' . $equals . '<br><br>';
//    <li>function count <br>
function lattice1($n1, $n2, $c){
    $lattice = array();
    $x = array();
    $y = array();
    for($i=1; $i<$c; $i++){
        $x = $n1[$i];
        $y = $n2[$i];
        $equals = $y * $x;
        echo $i . 'equals: ' . $equals .  '<br><br>';
        array_push($lattice, $equals);
    }
    var_dump($lattice);
    echo '<br>';
}

lattice1($cntX, $cntY, $counter);