Make two arrays from and array in php [duplicate] - php

Question

I have this array:
$array = array(a, b, c, d, e, f, g);
I want to split it in two arrays depending if the index is even or odd, like this:
$odd = array(a, c, e, g);
$even = array(b, d, f);
Thanks in advance!

Answer 1

One solution, using anonymous functions and array_walk:
$odd = array();
$even = array();
$both = array(&$even, &$odd);
array_walk($array, function($v, $k) use ($both) { $both[$k % 2][] = $v; });
This separates the items in just one pass over the array, but it's a bit on the "cleverish" side. It's not really any better than the classic, more verbose
$odd = array();
$even = array();
foreach ($array as $k => $v) {
if ($k % 2 == 0) {
$even[] = $v;
}
else {
$odd[] = $v;
}
}

Answer 2

Use array_filter (PHP >= 5.6):
$odd = array_filter($array, function ($input) {return $input & 1;}, ARRAY_FILTER_USE_KEY);
$even = array_filter($array, function ($input) {return !($input & 1);}, ARRAY_FILTER_USE_KEY);

Answer 3

I am not sure if this is the most elegant way, but it should work a charm:
$odd=array();
$even=array();
$count=1;
foreach($array as $val)
{
if($count%2==1)
{
$odd[]=$val;
}
else
{
$even[]=$val;
}
$count++;
}

Answer 4

As an almost-one-liner, I think this will be my favourite:
$even = $odd = array();
foreach( $array as $k => $v ) $k % 2 ? $odd[] = $v : $even[] = $v;
Or for a tiny little more? speed:
$even = $odd = array();
foreach( $array as $k => $v ) ( $k & 1 ) === 0 ? $even[] = $v : $odd[] = $v;
A bit more verbose variant:
$both = array( array(), array() );
// or, if $array has at least two elements:
$both = array();
foreach( $array as $k => $v ) $both[ $k % 2 ][] = $v;
list( $even, $odd ) = $both;
With array_chunk:
$even = $odd = array();
foreach( array_chunk( $array, 2 ) as $chunk ){
list( $even[], $odd[] ) = isset( $chunk[1]) ? $chunk : $chunk + array( null, null );
// or, to force even and odd arrays to have the same count:
list( $even[], $odd[] ) = $chunk + array( null, null );
}
If $array is guaranteed to have even number of elements:
$even = $odd = array();
foreach( array_chunk( $array, 2 ) as $chunk )
list( $even[], $odd[] ) = $chunk;
PHP 5.5.0+ with array_column:
$chunks = array_chunk( $array, 2 );
$even = array_column( $chunks, 0 );
$odd = array_column( $chunks, 1 );
Something similar for older PHP versions.
The keys will be 0,2,4,… and 1,3,5,…. If you don't like this, apply an array_values too:
$even = array_intersect_key( $array, array_flip( range( 0, count( $array ), 2 )));
$odd = array_intersect_key( $array, array_flip( range( 1, count( $array ), 2 )));
or
$even = array_intersect_key( $array, array_fill_keys( range( 0, count( $array ), 2 ), null ));
$odd = array_intersect_key( $array, array_fill_keys( range( 1, count( $array ), 2 ), null ));

Answer 5

One more functional solution with array_chunk and array_map. The last line removes empty item from the 2nd array, when size of a source array is odd
list($odd, $even) = array_map(null, ...array_chunk($ar,2));
if(count($ar) % 2) array_pop($even);

Answer 6

Just loop though them and check if the key is even or odd:
$odd = array();
$even = array();
foreach( $array as $key => $value ) {
if( 0 === $key%2) { //Even
$even[] = $value;
}
else {
$odd[] = $value;
}
}

Answer 7

One
$odd = $even = array();
for ($i = 0, $l = count($array ); $i < $l;) { // Notice how we increment $i each time we use it below, by two in total
$even[] = $array[$i++];
if($i < $l)
{
$odd[] = $array[$i++];
}
}
Two
$odd = $even = array();
foreach (array_chunk($array , 2) as $chunk) {
$even[] = $chunk[0];
if(!empty( $chunk[1]))
{
$odd[] = $chunk[1];
}
}

Answer 8

Based on #Jon's second variant, I made this following for use with PHP Smarty v3 template engine. This is for displaying news/blog with both one or two columns template model.
After the MySql query I'll do the following code :
if(sizeof($results) > 0) {
$data = array();
foreach($results as $k => $res) {
if($k % 2 == 0) {
$res["class"] = "even";
$data["all"][] = $data["even"][] = $res;
}
else {
$res["class"] = "odd";
$data["all"][] = $data["odd"][] = $res;
}
}
}
I obtain an array of 3 sub-arrays (including odd/even class) with Smarty syntax of use :
all items {foreach $data.all as $article}...{/foreach}
odd items only {foreach $data.odd as $article}...{/foreach}
even items only {foreach $data.even as $article}...{/foreach}
Hope it helps some people...

Answer 9

$odd = [];
$even = [];
while (count($arr)) {
$odd[] = array_shift($arr);
$even[] = array_shift($arr);
}

Answer 10

<?php
$array1 = array(0,1,2,3,4,5,6,7,8,9);
$oddarray = array();
$evenarray = array();
$count = 1;
echo "Original: ";
foreach ($array1 as $value)
{
echo "$value";
}
echo "<br> Even: ";
foreach ($array1 as $print)
{
if ($count%2==1)
{
$evenarray = $print;
echo "$print";
}
$count++;
}
echo "<br> Odd: ";
foreach ($array1 as $print2) {
if ($count%2!=1)
{
$oddarray[] = $print2;
echo "$print2";
}
$count++;
}
?>
Output:
Original: 0123456789
Even: 02468
Odd: 13579