Detailed explanation of PHP maze generation and automatic pathfinding algorithm

class Maze{
    // Maze Create
    private $_w;
    private $_h;
    private $_grids;
    private $_walkHistory;
    private $_walkHistory2;
    private $_targetSteps;
    // Construct
    public function Maze() {
        $this->_w = 6;
        $this->_h = 6;
        $this->_grids = array();
    }
    // 设置迷宫大小
    public function set($width = 6, $height = 6) {
        if ( $width > 0 ) $this->_w = $width;
        if ( $height > 0 ) $this->_h = $height;
        return $this;
    }
    // 取到迷宫
    public function get() {
        return $this->_grids;
    }
    // 生成迷宫
    public function create() {
        $this->_init();
        return $this->_walk(rand(0, count($this->_grids) -1 ));
    }
    // 获取死胡同点
    public function block($n = 0, $rand = false) {
        $l = count($this->_grids);
        for( $i = 1; $i < $l; $i++ ) {
            $v = $this->_grids[$i];
            if ( $v == 1 || $v == 2 || $v == 4 || $v == 8 ) {
                $return[] = $i;
            }
        }
        // 随机取点
        if ( $rand ) shuffle($return);
 
        if ( $n == 0 ) return $return;
 
        if ( $n == 1 ) {
            return array_pop($return);
        } else {
            return array_slice($return, 0, $n);
        }
    }
    /**
    |---------------------------------------------------------------
    | 生成迷宫的系列函数
    |---------------------------------------------------------------
    */
    private function _walk($startPos) {
        $this->_walkHistory = array();
        $this->_walkHistory2 = array();
        $curPos = $startPos;
        while ($this->_getNext0() != -1) {
            $curPos = $this->_step($curPos);
            if ( $curPos === false ) break;
        }
        return $this;
    }
    private function _getTargetSteps($curPos) {
        $p = 0;
        $a = array();
        $p = $curPos - $this->_w;
        if ($p > 0 && $this->_grids[$p] === 0 && ! $this->_isRepeating($p)) {
            array_push($a, $p);
        } else {
            array_push($a, -1);
        }
        $p = $curPos + 1;
        if ($p % $this->_w != 0 && $this->_grids[$p] === 0 && ! $this->_isRepeating($p)) {
            array_push($a, $p);
        } else {
            array_push($a, -1);
        }
        $p = $curPos + $this->_w;
        if ($p < count($this->_grids) && $this->_grids[$p] === 0 && ! $this->_isRepeating($p)) {
            array_push($a, $p);
        } else {
            array_push($a, -1);
        }
        $p = $curPos - 1;
        if (($curPos % $this->_w) != 0 && $this->_grids[$p] === 0 && ! $this->_isRepeating($p)) {
            array_push($a, $p);
        } else {
            array_push($a, -1);
        }
        return $a;
    }
    private function _noStep() {
        $l = count($this->_targetSteps);
        for ($i = 0; $i < $l; $i ++) {
            if ($this->_targetSteps[$i] != -1) return false;
        }
        return true;
    }
    private function _step($curPos) {
        $this->_targetSteps = $this->_getTargetSteps($curPos);
        if ( $this->_noStep() ) {
            if ( count($this->_walkHistory) > 0 ) {
                $tmp = array_pop($this->_walkHistory);
            } else {
                return false;
            }
            array_push($this->_walkHistory2, $tmp);
            return $this->_step($tmp);
        }
        $r = rand(0, 3);
        while ( $this->_targetSteps[$r] == -1) {
            $r = rand(0, 3);
        }
        $nextPos = $this->_targetSteps[$r];
        $isCross = false;
        if ( $this->_grids[$nextPos] != 0)
            $isCross = true;
        if ($r == 0) {
            $this->_grids[$curPos] ^= 1;
            $this->_grids[$nextPos] ^= 4;
        } elseif ($r == 1) {
            $this->_grids[$curPos] ^= 2;
            $this->_grids[$nextPos] ^= 8;
        } elseif ($r == 2) {
            $this->_grids[$curPos] ^= 4;
            $this->_grids[$nextPos] ^= 1;
        } elseif ($r == 3) {
            $this->_grids[$curPos] ^= 8;
            $this->_grids[$nextPos] ^= 2;
        }
        array_push($this->_walkHistory, $curPos);
        return $isCross ? false : $nextPos;
    }
    private function _isRepeating($p) {
        $l = count($this->_walkHistory);
        for ($i = 0; $i < $l; $i ++) {
            if ($this->_walkHistory[$i] == $p) return true;
        }
        $l = count($this->_walkHistory2);
        for ($i = 0; $i < $l; $i ++) {
            if ($this->_walkHistory2[$i] == $p) return true;
        }
        return false;
    }
    private function _getNext0() {
        $l = count($this->_grids);
 
        for ($i = 0; $i <= $l; $i++ ) {
            if ( $this->_grids[$i] == 0) return $i;
        }
        return -1;
    }
    private function _init() {
        $this->_grids = array();
        for ($y = 0; $y < $this->_h; $y ++) {
            for ($x = 0; $x < $this->_w; $x ++) {
                array_push($this->_grids, 0);
            }
        }
        return $this;
    }
}

class AStar{
    // A-star
    private $_open;
    private $_closed;
    private $_start;
    private $_end;
    private $_grids;
    private $_w;
    private $_h;
    // Construct
    public function AStar(){
        $this->_w = null;
        $this->_h = null;
        $this->_grids = null;
    }
    public function set($width, $height, $grids) {
        $this->_w = $width;
        $this->_h = $height;
        $this->_grids = $grids;
        return $this;
    }
    // 迷宫中寻路
    public function search($start = false, $end = false) {
        return $this->_search($start, $end);
    }
    /**
    |---------------------------------------------------------------
    | 自动寻路 - A-star 算法
    |---------------------------------------------------------------
    */
    public function _search($start = false, $end = false) {
        if ( $start !== false ) $this->_start = $start;
        if ( $end !== false ) $this->_end = $end;
        $_sh = $this->_getH($start);
        $point['i'] = $start;
        $point['f'] = $_sh;
        $point['g'] = 0;
        $point['h'] = $_sh;
        $point['p'] = null;
        $this->_open[] = $point;
        $this->_closed[$start] = $point;
        while ( 0 < count($this->_open) ) {
            $minf = false;
            foreach( $this->_open as $key => $maxNode ) {
                if ( $minf === false || $minf > $maxNode[&#39;f&#39;] ) {
                    $minIndex = $key;
                }
            }
            $nowNode = $this->_open[$minIndex];
            unset($this->_open[$minIndex]);
            if ( $nowNode[&#39;i&#39;] == $this->_end ) {
                $tp = array();
                while( $nowNode[&#39;p&#39;] !== null ) {
                    array_unshift($tp, $nowNode[&#39;p&#39;]);
                    $nowNode = $this->_closed[$nowNode[&#39;p&#39;]];
                }
                array_push($tp, $this->_end);
                break;
            }
            $this->_setPoint($nowNode[&#39;i&#39;]);
        }
        $this->_closed = array();
        $this->_open = array();
        return $tp;
    }
    private function _setPoint($me) {
        $point = $this->_grids[$me];
        // 所有可选方向入队列
        if ( $point & 1 ) {
            $next = $me - $this->_w;
            $this->_checkPoint($me, $next);
        }
        if ( $point & 2 ) {
            $next = $me + 1;
            $this->_checkPoint($me, $next);
        }
        if ( $point & 4 ) {
            $next = $me + $this->_w;
            $this->_checkPoint($me, $next);
        }
        if ( $point & 8 ) {
            $next = $me - 1;
            $this->_checkPoint($me, $next);
        }
    }
    private function _checkPoint($pNode, $next) {
        if ( $this->_closed[$next] ) {
            $_g = $this->_closed[$pNode][&#39;g&#39;] + $this->_getG($next);
            if ( $_g < $check[&#39;g&#39;] ) {
                $this->_closed[$next][&#39;g&#39;] = $_g;
                $this->_closed[$next][&#39;f&#39;] = $this->_closed[$next][&#39;g&#39;] + $this->_closed[$next][&#39;h&#39;];
                $this->_closed[$next][&#39;p&#39;] = $pNode;
            }
        } else {
            $point[&#39;p&#39;] = $pNode;
            $point[&#39;h&#39;] = $this->_getH($next);
            $point[&#39;g&#39;] = $this->_getG($next);
            $point[&#39;f&#39;] = $point[&#39;h&#39;] + $point[&#39;g&#39;];
            $point[&#39;i&#39;] = $next;
            $this->_open[] = $point;
            $this->_closed[$next] = $point;
        }
    }
    private function _getG($point) {
        return abs($this->_start - $point);
    }
    private function _getH($point) {
        return abs($this->_end - $point);
    }
}