<?php

$arrs = [
  [1, 5, 1],
  [3, 2, 7, 5, 4],
  [4, 3, 6, 5],
];

$result = [];
$num_arrs = count($arrs);
for($i = 0; $i < $num_arrs; $i++){
  $size = count($arrs[$i]);
  for($j = 0; $j < $size; $j++){
    if(!isset($result[$j]))
      $result[$j] = [];
    $result[$j][] = $arrs[$i][$j];
  }
}

print_r($result);