php get sub array from an array - php

Question

here is an array and I want to extract "category_input" as sub array. This sub array contains "cat_id" and "post-titles". Then I will want to insert the posts into WordPress DB under each category. is. cat_20 will have posts named as post-in-cat-20 and so on.
Array
(
[post_type] => post
[post_status] => publish
[content_texarea] =>
[category_input] => Array
(
[0] => cat_20
[1] => post-in-cat-20
[2] => post-in-cat-20
[3] => post-in-cat-20
[4] => cat_19
[5] => post-in-cat-19
[6] => post-in-cat-19
[7] => post-in-cat-19
[8] => post-in-cat-19
[9] => cat_2
[10] => post-in-cat-2
[11] => post-in-cat-2
[12] => post-in-cat-2
)
)
Expected Results
extracted array will be as
[category_input] => Array
(
[0] => cat_20
[1] => post-in-cat-20
[2] => post-in-cat-20
[3] => post-in-cat-20
[4] => cat_19
[5] => post-in-cat-19
[6] => post-in-cat-19
[7] => post-in-cat-19
[8] => post-in-cat-19
[9] => cat_2
[10] => post-in-cat-2
[11] => post-in-cat-2
[12] => post-in-cat-2
)
Then, I will need to make caegory and posts array to use in wp query
[category_input] => Array
(
[cat_20] => Array
[1] => post-in-cat-20
[2] => post-in-cat-20
[3] => post-in-cat-20
[cat_19] => Array
[5] => post-in-cat-19
[6] => post-in-cat-19
[7] => post-in-cat-19
[8] => post-in-cat-19
[cat_2] => Array
[10] => post-in-cat-2
[11] => post-in-cat-2
[12] => post-in-cat-2
)

Answer 1

As you want to update the portion of your array- take a look at the given parts.
The array from the main array by $main_arr[category_input];
foreach($category_input as $val){
$part = explode('_', $val);
if(isset($part[0]) && $part[0] == 'cat'){
$out_arr[$val] = array();
$key = $val;
}else{
$out_arr[$key][] = $val;
}
}
Look at the complete example: https://3v4l.org/JI9U7
Now you can put the $out_arr again to the $main_arr.