How to operate two-dimensional array matrix transpose in PHP

<?php
  $arr1 = array(
        array(1,2,3),
        array(4,5,6),
        array(6,7,8),
        array(&#39;a&#39;,&#39;b&#39;,&#39;c&#39;)
      );
  echo &#39;脚本之家测试结果:<br><br>&#39;;
  echo &#39;矩阵转置前:<br>&#39;;
  for($i=0;$i<count($arr1);$i++){
    for($j=0;$j<count($arr1[$i]);$j++){
     echo $arr1[$i][$j].&#39; &#39;;
    }
    echo &#39;<br>&#39;;
  }
  echo &#39;矩阵转置后:<br>&#39;;
  for($i=0;$i<count($arr1);$i++){      //确定转置列数
    for($j=0;$j<count($arr1[$i]);$j++){  //确定转置行数
     $arr2[$j][$i] = $arr1[$i][$j];   //将矩阵1的“第i行第j列”的值 赋给 矩阵2的“第j行第i列”
    }
  }
  for($j=0;$j<count($arr2);$j++){       //遍历数组2
    for($i=0;$i<count($arr2[$j]);$i++){
     echo $arr2[$j][$i].&#39; &#39;;
    }
    echo &#39;<br>&#39;;
  }
?>