http://cslai.coolsilon.com/2014/09/12/spiraling-number/

spiral.php

#!/usr/bin/env php
<?php

function node_is_valid($count_row, $count_column, Array $node_path, $node_next) {
    return FALSE === (node_is_used($node_next, $node_path)
        OR node_exceeds_range($node_next, $count_row, $count_column));
}

function node_is_used($node_next, $node_path) {
    return in_array($node_next, $node_path); 
}

function node_exceeds_range($node_next, $count_row, $count_column) {
    return $node_next[0] >= $count_row
        OR $node_next[0] < 0
        OR $node_next[1] >= $count_column
        OR $node_next[1] < 0;
}

function node_candidates(Array $node_path) {
    $node_last = end(array_values($node_path));
    $node_vector = node_get_vector($node_path, $node_last);

    return array(
        node_go_to($node_last, $node_vector),
        node_go_to($node_last, node_rotate_vector($node_vector)));
}

function node_get_vector($node_path, $node_last) {
    $node_count = count($node_path);

    return $node_count > 1 ?
        array($node_last[0] - $node_path[$node_count - 2][0],
            $node_last[1] - $node_path[$node_count - 2][1])
        : array(0, 1);
}

function node_rotate_vector($node_vector) {
    // maths theorem by @angch
    // http://en.wikipedia.org/wiki/Rotation_matrix#Common_rotations
    return array($node_vector[1], -1 * $node_vector[0]);
}

function node_go_to($node_last, $node_vector) {
    return array($node_last[0] + $node_vector[0],
        $node_last[1] + $node_vector[1]);
}

function node_get_next($row, $column, Array $node_path) {
    return array_shift(array_filter(
        node_candidates($node_path),
        function($node_next) use($row, $column, $node_path) {
            return node_is_valid($row, $column, $node_path, $node_next);
        }));
}

function node_construct_path($row, $column, $node_path=array(array(0, 0))) {
    return count($node_path) == ($row * $column) ?
        $node_path
        : node_construct_path(
            $row,
            $column,
            array_merge(
                $node_path,
                array(node_get_next($row, $column, $node_path))));
}

function print_result($row_count, $column_count, Array $result) {
    $format = sprintf('%%%dd ', strlen($row_count * $column_count));
    $column_range = range(0, $column_count - 1);

    array_walk(range(0, $row_count - 1), function($row) use($column_range, $format, $result) {
        array_walk($column_range, function($column) use($row, $format, $result) {
            printf($format, 1 + array_search(array($row, $column), $result));
        });

        echo PHP_EOL;
    });
}

function spiral($row, $column) {
    return print_result($row, $column, node_construct_path($row, $column));
}

spiral(5,5);