<?php

//stick it in a while loop so you don't have to keep re-running
while (1) {

    //initialize the triangle array
    $triangle = array();

    echo "INPUT ZERO-BASED COORDINATES\n";

    // open a handle to standard input in read mode, get the first line.
    $handle = fopen("php://stdin", "r");
    $line = fgets($handle);

    //split it up by the comma.
    $coords = explode(',', trim($line));

    // if the numbers are anything but digits, it's not a valid input.
    // could probably use preg_ functions to do all input matching (forget explode)
    // but I'm too lazy.
    if (!preg_match('/^\d+$/', $coords[0]) && !preg_match('/^\d+$/', $coords[1])) {
        die("INVALID INPUT\n");
    }

    //get the result
    $result = calculate($coords[1], $coords[0]);
    echo "RESULT: " . $result . "\n";

    // Get the string length of $result, pad all other results to this size
    $numsize = strlen($result);

    // render the triangle.
    for ($y = 0; $y <= $coords[0]; $y++) {
        // for every row go through all the values
        for ($x = 0; $x <= $y; $x++) {
            //if this has a value, pad it to $numsize
            //otherwise output asterisks
            if (isset($triangle[$y][$x])) {
                $padded_item = str_pad($triangle[$y][$x], $numsize, " ");
                echo $padded_item . " ";
            } else
                echo str_repeat("*", $numsize) . " ";
        }
        echo "\n";
    }
}

// Calculate a point on the pascal's triangle
// takes zero based x and y ints
function calculate($x, $y) {
    // grab that triangle out of the global scope
    global $triangle;

    // if it's the first or last value in a row, it'll be 1.
    if (($x == 0) || ($x == $y)) {
        return 1;
    }
    // if it's outside of the row's values it'll be a zero
    // there could be some argument to this, but I feel pretty secure in
    // considering this to be the case.
    if ($x > $y) {
        return 0;
    }

    // if the value directly above the target value is undefined, perform a calculate() on it
    if (!isset($triangle[$y - 1][$x])) {
        calculate($x, $y - 1);
    }
    // same as above but for the value above and one to the left.
    if (!isset($triangle[$y - 1][$x - 1])) {
        calculate($x - 1, $y - 1);
    }

    // define this location on the triangle and return it.
    $triangle[$y][$x] = $triangle[$y - 1][$x] + $triangle[$y - 1][$x - 1];
    return $triangle[$y][$x];
}

?>