PHP how to merge arrays?

Question

How can I merge multiple arrays into one that have same column. My codes are like

$stmt1 = $pdo ->prepare('SELECT * FROM `formsone`');
$stmt1 ->execute();
$applications1 = $stmt1 ->fetchAll();
$stmt2 = $pdo ->prepare('SELECT * FROM `formstwo`');
$stmt2 ->execute();
$applications2 = $stmt2 ->fetchAll();
$stmt3 = $pdo ->prepare('SELECT * FROM `formsthree`');
$stmt3 ->execute();
$applications3 = $stmt3 ->fetchAll();
$stmt4 = $pdo ->prepare('SELECT * FROM `formsfour`');
$stmt4 ->execute();
$applications4 = $stmt4 ->fetchAll();
$results = // Merge all applications into one

They all have same columns like id , name , password , I just want to combine all of the results into one.

Answer 1

Ok let's assume that you have 4 arrays:

<?php

$data1=[
    'id' => 1,
    'name' => 'test1',
    'password' => 'pass1'

];

$data2=[
    'id' => 2,
    'name' => 'test2',
    'password' => 'pass2'

];

$data3=[
    'id' => 3,
    'name' => 'test3',
    'password' => 'pass3'

];

$data4=[
    'id' => 4,
    'name' => 'test4',
    'password' => 'pass4'

];

They all have the same fields as you mentioned. In order to merge them you can use:

$result=array_merge_recursive($data1,$data2,$data3,$data4);
echo '<pre>';
print_r($result);

The output will be a new array including all the merged data based on the key values of each array:

Array
(
    [id] => Array
        (
            [0] => 1
            [1] => 2
            [2] => 3
            [3] => 4
        )

    [name] => Array
        (
            [0] => test1
            [1] => test2
            [2] => test3
            [3] => test4
        )

    [password] => Array
        (
            [0] => pass1
            [1] => pass2
            [2] => pass3
            [3] => pass4
        )

)

In this example array_merge will not work properly because while creating the new array it will override the data because of the same array_key (id,name,password in our example). That's why i used array_merge_recursive which created a multi-dimensional array based on the key values.