php merge associative arrays by key code example

Example 1: array merge in php

/* 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.
*/

Example 2: php array merge for associative arrays

<?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.

Example 3: php merge array with same value

function custom_array_merge(&$array1, &$array2) {
    $result = Array();
    foreach ($array1 as $key_1 => &$value_1) {
        // if($value['name'])
        foreach ($array2 as $key_1 => $value_2) {
            if($value_1['name'] ==  $value_2['name']) {
                $result[] = array_merge($value_1,$value_2);
            }
        }

    }
    return $result;
}

Example 4: array merge with same key in php

Input : $a1=array("a"=>"raj", "b"=>"striver");
        $a2=array("z"=>"geeks", "b"=>"articles");
Output : 
Array
(
    [a] => raj
    [b] => Array
        (
            [0] => striver
            [1] => articles
        )

    [z] => geeks
)