BFS algorithm using PHP

bfs.php

<?php

$maze = '
1111111
1000001
10S1001
1001001
10000E1
1000001
1111111
';

function str2dmap($str) {
    $lines = explode("\n", trim($str));
    return array_map('str_split', $lines);
}

function find2dmap($map, $v)
{
    for($x = 0; $x < count($map); $x++) {
        $line = $map[$x];
        for($y = 0; $y < count($line); $y++) {
            if($line[$y] === $v) {
                return [$x, $y];
            }
        }
    }
}

// install php 7.2 and php-ds, or make your own Queue class
function find_path($map, $begin, $end, $QueueClass='\Ds\Queue') {
    error_reporting(E_ALL ^ E_NOTICE);
    $q = new $QueueClass; // \Ds\Queue or \Ds\Stack
    $q->push($begin);
    $flag = $map;
    $btrace = $map;
    list($bx, $by) = $begin;
    list($ex, $ey) = $end;

    while(!$q->isEmpty()) {
        list($x, $y, $prev) = $q->pop();

        // visit every point only once
        if($flag[$x][$y] === true) continue;
        $flag[$x][$y] = true;

        // we hit a wall
        if($map[$x][$y] === '1') continue;

        // record previous point
        $btrace[$x][$y] = $prev;

        // visit the points around current point
        $current = [$x, $y];
        $q->push([$x - 1, $y, $current]);
        $q->push([$x + 1, $y, $current]);
        $q->push([$x, $y - 1, $current]);
        $q->push([$x, $y + 1, $current]);

        // is it end?
        if($x === $ex && $y === $ey) {
            // back trace the path
            $ret = [$current];

            while($prev) {
                $ret[] = $prev;
                list($x, $y) = $prev;
                $prev = $btrace[$x][$y];
            }

            return array_reverse($ret);
        }
    }
}

echo $maze;
$map = str2dmap($maze);
$begin = find2dmap($map, 'S');
$end = find2dmap($map, 'E');

printf("Start at (%d, %d)\n", $begin[0], $begin[1]);
printf("End   at (%d, %d)\n", $end[0], $end[1]);

$path = find_path($map, $begin, $end);
printf("Path: %s\n", json_encode($path));

output.txt

[ 02/21 02:09:36 ] inndy @ Fireball ~ (N/A)
$ php bfs.php

1111111
1000001
10S1001
1001001
10000E1
1000001
1111111
Start at (2, 2)
End   at (4, 5)
Path: [[2,2],[3,2],[4,2],[4,3],[4,4],[4,5]]