PHP merge array variations

gistfile1.txt

<?php
// Existing array 
$arr = array(1, 2, 3); 
          
// New element to be added at 'zero' => 0 
  
// Create an array using the new element 
$temp = array('one');
$temp2 = array("hhhhhh");
      
// Append the $temp in the beginning of $arr 
      
// Using array union(+) operator 

echo "Result of array union(+) : "; 
print_r([...$temp, ...$arr, ...$temp2]);

echo "Result of array union(+) : "; 
$arr2 = $temp + $arr + $temp2; 
print_r($arr2); 


echo "Result merge"; 
print_r(array_merge($arr, $temp));