php array_merge

<?php
$array1 = array("color" => "red", 2, 4);
$array2 = array("a", "b", "color" => "green", "shape" => "trapezoid", 4);
$result = array_merge($array1, $array2);
print_r($result);
?>
Array
(
    [color] => green
    [0] => 2
    [1] => 4
    [2] => a
    [3] => b
    [shape] => trapezoid
    [4] => 4
)

<?php

 $a1=array("red","green");
$a2=array("blue","yellow");
print_r(array_merge($a1,$a2));

?>
 

/* Array merge is basically use to merge the two array data. */
  
<?php
$a1=array("red","green");
$a2=array("blue","green","yellow");
print_r(array_merge($a1,$a2));
?>
  
/*
Output:
Array ( [0] => red [1] => green [2] => blue [3] => green [4] => yellow )
*/
  
<?php
$a1=array("a"=>"red","b"=>"green");
$a2=array("c"=>"blue","b"=>"yellow");
print_r(array_merge($a1,$a2));
?>

/*
Output:
Array ( [a] => red [b] => yellow [c] => blue )
*/
  
/* In above example you can check the difference in output 
it takes all values of both array in final output, but not in associative array you can check.
because one value gets overwritten by same key reference in both array.
*/

<?php

$array1 = array('key1' => 'test1', 'key2' => 'test2');
$array2 = array('key3' => 'test3', 'key4' => 'test4');

$resultArray = array_merge($array1, $array2);

// If you have numeric or numeric like keys, array_merge will 
// reset the keys to 0 and start numbering from there

$resultArray = $array1 + $array2;

// Using the addition operator will allow you to preserve your keys,
// however any duplicate keys will be ignored.

$output = array_merge($array1, $array2);

<?php
  $array1 = [
      "color" => "green"
  ];
  $array2 = [
      "color" => "red", 
      "color" => "blue"
  ];
  $result = array_merge($array1, $array2);
?>

// $result
[
    "color" => "green"
    "color" => "red", 
    "color" => "blue"
]

<?php
$array1    = array("color" => "red", 2, 4);
$array2    = array("a", "b", "color" => "green", "shape" => "trapezoid", 4);
$resultado = array_merge($array1, $array2);
print_r($resultado);
?>

array_merge ([ array $... ] ) : array

Combina los elementos de uno o más arrays juntándolos de modo que los valores de uno se anexan al final del anterior. Retorna el array resultante.