How to flatten array in PHP? - php

Question

I have an array that contains 4 arrays with one value each.
array(4) {
[0]=>
array(1) {
["email"]=>
string(19) "test01#testmail.com"
}
[1]=>
array(1) {
["email"]=>
string(19) "test02#testmail.com"
}
[2]=>
array(1) {
["email"]=>
string(19) "test03#testmail.com"
}
[3]=>
array(1) {
["email"]=>
string(19) "test04#testmail.com"
}
}
What is the best (=shortest, native PHP functions preferred) way to flatten the array so that it just contains the email addresses as values:
array(4) {
[0]=>
string(19) "test01#testmail.com"
[1]=>
string(19) "test02#testmail.com"
[2]=>
string(19) "test03#testmail.com"
[3]=>
string(19) "test04#testmail.com"
}

Answer 1

In PHP 5.5 you have array_column:
$plucked = array_column($yourArray, 'email');
Otherwise, go with array_map:
$plucked = array_map(function($item){ return $item['email'];}, $yourArray);

Answer 2

You can use a RecursiveArrayIterator . This can flatten up even multi-nested arrays.
<?php
$arr1=array(0=> array("email"=>"test01#testmail.com"),1=>array("email"=>"test02#testmail.com"),2=> array("email"=>"test03#testmail.com"),
3=>array("email"=>"test04#testmail.com"));
echo "<pre>";
$iter = new RecursiveIteratorIterator(new RecursiveArrayIterator($arr1));
$new_arr = array();
foreach($iter as $v) {
$new_arr[]=$v;
}
print_r($new_arr);
OUTPUT:
Array
(
[0] => test01#testmail.com
[1] => test02#testmail.com
[2] => test03#testmail.com
[3] => test04#testmail.com
)