array_filter function in function - php

Question

I have this function, where a array_filter function is included:
$var = "test";
function mainFunction() {
global $var;
$myNewArray = array();
$data = array("a", "b", "c");
array_filter($data, function ($value) {
global $myNewArray;
$myNewArray[] = $value;
});
print_r($myNewArray); // TEST OUTPUT
}
mainFunction();
Problem:
My test output myNewArray is empty.
I know that my array_filter function is senless at the moment until I check no values.
But only for testing, I would like to use it, to create a newArray. But this doesn't work. Where is my mistake?
UPDATE
I updated my code:
function mainFunction() {
global $var;
$myNewArray = array();
$data[] = array("id" => "1", "content" => "Hello");
$data[] = array("id" => "2", "content" => "World");
$myNewArray = array_filter($data, function ($value) {
if ($value['content'] == "World") {
return $value['content'];
}
});
print_r($myNewArray); // TEST OUTPUT
}
mainFunction();
This works, but not correctly.
I would like to save only the content value.
But my $myNewArray looks like this:
Array
(
[0] => Array
(
[id] => 2
[content] => World
)
)
Instead of
Array
(
[0] => Array
(
[content] => World
)
)

Answer 1

I would combine array_filter and array_map for this.
$data[] = array("id" => "1", "content" => "Hello");
$data[] = array("id" => "2", "content" => "World");
// filter the data
$data = array_filter($data, fn ($value) => $value['content'] === 'World');
// map the data
$data = array_map(fn ($value) => ['content' => $value['content']], $data);
// reset indexes
$data = array_values($data);
print_r($data);
Example: https://phpize.online/s/9U

Answer 2

Everything seems to work fine.
<?php
$data = [];
$data[] = array("id" => "1", "content" => "Hello");
$data[] = array("id" => "2", "content" => "World");
$filtered_data = array_filter($data, function($value) {
return $value['content'] == "World";
});
print_r($filtered_data);
The output is just like expected:
Array (
[1] => Array
(
[id] => 2
[content] => World
)
)
But if you want to leave only some fields in resulting array, array_filter will not help you (at least without a crutch).
You may want to iterate source array and filter it by yourself.
<?php
$data = [];
$data[] = array("id" => "1", "content" => "Hello");
$data[] = array("id" => "2", "content" => "World");
$filtered_data = [];
foreach($data as $v) {
if($v['content'] == "World")
$filtered_data[] = ["content" => $v['content']];
}
print_r($filtered_data);
The output then would be:
Array (
[0] => Array
(
[content] => World
)
)

Answer 3

You want two different things :
filter your array (keep only some elements)
map your array (change the value of each element)
Filter your array
On your second attempt you've done it right but array_filter callback function expect a boolean as the return value. It will determine wherever array_filter need to keep the value or not.
Map your array
You need to remove all value on each element except the "content" value. You can use array_map to do that.
function mainFunction() {
$data[] = array("id" => "1", "content" => "Hello");
$data[] = array("id" => "2", "content" => "World");
$myNewArray = array_filter($data, function ($value) {
if ($value['content'] == 'World') {
return true;
}
return false;
});
// myNewArray contains now the willing elements, but still don't have the willing format
/* myNewArray is [
0 => [
'id' => '2',
'content' => 'World'
]
]*/
$myNewArray = array_map($myNewArray, function($value){
return [
'content' => $value['content']
];
});
// myNewArray contains now the willing elements with the willing format
/* myNewArray is [
0 => [
'content' => 'World'
]
] */
}
mainFunction();

Answer 4

In mainFunction you are not using $myNewArray as global so it's only in the scope, but in the array_filter function you are using global $myNewArray;
$var = "test";
$myNewArray; // global array
function mainFunction() {
global $var, $myNewArray;//if this is not present it's not global $myNewArray
$myNewArray = array();
$data = array("a", "b", "c");
array_filter($data, function ($value) {
global $myNewArray;//this uses global
$myNewArray[] = $value;
});
print_r($myNewArray); // TEST OUTPUT
}
mainFunction();
Here is an example of you code without global $myNewArray
$var = "test";
function mainFunction($var) {
$myNewArray = array();
$data = array("a", "b", "c");
$myNewArray[] = array_filter($data, function ($value) {
return $value;
});
print_r($myNewArray); // TEST OUTPUT
}
mainFunction($var);
Answer to Update:
You can use array_reduce to achieve that
function mainFunction() {
global $var;
$myNewArray = array();
$data[] = array("id" => "1", "content" => "Hello");
$data[] = array("id" => "2", "content" => "World");
$myNewArray = array_reduce($data, function($accumulator, $item) {
if ($item['content'] === "World")
$accumulator[] = ['content' => $item['content']];
return $accumulator;
});
print_r($myNewArray); // TEST OUTPUT
}
mainFunction();

Answer 5

you can use this code..........
<?php
function test_odd($var)
{
return($var & 1);
}
$a1=array(1,3,2,3,4);
print_r(array_filter($a1,"test_odd"));
?>