An algo to replace all the natural numbers with zero (horizontally and vertically).

matrix.php

<?php
/**
 * This is an algo to replace all the natural numbers with zero (horizontally and vertically).
 * This was an interview question to solve.
 *
 * If you have more better solution with less iteration will be appreciated.
 *
 * @author Mohammed Mudasir <[email protected]>
 **/

// Actual matrix
$matrix = [
	[1, 3, 5, 7],
	[9, 0, 4, 2],
	[8, 4, 10, 1],
	[9, 5, 1, 0],
];

// expected matrix
/**
 *
 * $matrix = [
 *	  [1, 0, 5, 0],
 *	  [0, 0, 0, 0],
 *	  [8, 0, 10, 0],
 *	  [0, 0, 0, 0],
 * ];
 *
 **/

// Indexes will be store when ever "0" occurrence found.
$indexes = [];

// Looping to get indexes
foreach ($matrix as $row) {
	foreach ($row as $key => $value) {
		if ($value == 0) {
			$indexes[] = $key;
		}
	}
}

// Only store unique indexes also getting only values out and fliping it to store as a key. 
$indexes = array_flip(array_values(array_unique($indexes)));

// Start actual matrix iteration
foreach ($matrix as $matrixKey => $row) {

	// If 0 is found in a row then replace whole row with zero
	if (in_array(0, $row)) {
		$matrix[$matrixKey] = array_fill(0, count($row), 0);

		continue;
	}

	// Looping in a row to find zero is found in our store index $index
	foreach ($row as $key => $value) {
		if (isset($indexes[$key])) {
			$matrix[$matrixKey][$key] = 0;
		}
	}
}

print_r($matrix);