<?php

function minhaMatriz($cols = 5)
{
    $data = array_fill(0, $cols, array_fill(0, $cols, 0));

    foreach($data as $i => $items) {
        foreach($items as $j => $item) {
            if ($i == $j || $i == 0) {
                $data[$j][$i] = 1;
            } else {
                $data[$j][$i] = $item;
            }
        }
    }

    return $data;
}

foreach(minhaMatriz() as $items) {
    foreach($items as $item) {
        echo $item;
    }

    echo "\n";
}

/*
  Default(5):

  1 0 0 0 0
  1 1 0 0 0
  1 0 1 0 0
  1 0 0 1 0
  1 0 0 0 1
*/