<?php
$array = array_fill(0, 10, array_fill(0, 10, '_'));

$array[0][0] = '1';

$i = 0;

foreach($array as $y => $x) {
	foreach($x as $key => &$value) {
		$array[$y][$key] = $i;
		
		$i++;
	}
}


foreach ($array as $y => $x) {
	foreach ($x as $key => $value) {
		echo ' ' . $value . ' ';
	}

	echo "\n";
}