how to make a multidimension array in php code example

Example 1: convert multidimensional array to single array php

$singleArray = []; 
foreach ($parentArray as $childArray) 
{ 
    foreach ($childArray as $value) 
    { 
    $singleArray[] = $value; 
    } 
}

Example 2: how to create multidimensional array in php

$cars = array
  (
  array("Volvo",22,18),
  array("BMW",15,13),
  array("Saab",5,2),
  array("Land Rover",17,15)
  );