Filter - Odd Even

Question

How can I filter array entries with an odd or even index number?

Array ( [0] => string1 [1] => string2 [2] => string3 [3] => string4 ) 

Like, I want to remove entries from [0] and [2] from an array. Or to say that I have 0,1,2,3,4,5,6,7,8,9 - I will need to remove 0,2,4,6,8.

Answer 1

foreach($arr as $key => $value) if($key&1) unset($arr[$key]);

The above removes the positions of an odd number from the array, to remove the even positions of the positions, use the following:

Instead of if($key&1) you can use if(!($key&1))

Answer 2

Here's the "hax" solution:

Use array_filter in conjunction with the isodd function.

array_filter seems to work only with values, so you can first array_flip and then use array_filter.

 array_flip(array_filter(array_flip($data), create_function('$a','return $a%2;'))) 

Answer 3

You can also use SPL FilterIterator as follows:

 class IndexFilter extends FilterIterator { public function __construct (array $data) { parent::__construct(new ArrayIterator($data)); } public function accept () { # return even keys only return !($this->key() % 2); } } $arr = array('string1', 'string2', 'string3', 'string4'); $filtered = array(); foreach (new IndexFilter($arr) as $key => $value) { $filtered[$key] = $value; } print_r($filtered); 

Answer 4

 <?php function odd($var) { // returns whether the input integer is odd return($var & 1); } function even($var) { // returns whether the input integer is even return(!($var & 1)); } $array1 = array("a"=>1, "b"=>2, "c"=>3, "d"=>4, "e"=>5); $array2 = array(6, 7, 8, 9, 10, 11, 12); echo "Odd :\n"; print_r(array_filter($array1, "odd")); echo "Even:\n"; print_r(array_filter($array2, "even")); ?> Odd : Array ( [a] => 1 [c] => 3 [e] => 5 ) Even: Array ( [0] => 6 [2] => 8 [4] => 10 [6] => 12 ) 

Answer 5

I would do it like this ...

 for($i = 0; $i < count($array); $i++) { if($i % 2) // OR if(!($i % 2)) { unset($array[$i]); } } 

Answer 6

 <?php $array = array(0, 3, 5, 7, 20, 10, 99,21, 14, 23, 46); for ($i = 0; $i < count($array); $i++) { if ($array[$i]%2 !=0) echo $array[$i]."<br>"; } ?>