Hope this is what you expect.
Happy coding .. :)

<?php
$permissions = ['create_user', 'create_post','edit_post', 'delete_post', 'edit_user', 'delete_user'];
$permission_categories = [];
$set = [];
        
foreach ($permissions as $permission) {
   $name = explode("_", $permission);
   $key = $name[1];
   $value = $name[0];

    if (!array_key_exists($key, $permission_categories)) {
        $permission_categories[$key] = [$value];
    }else{
         array_push($permission_categories[$key],$value);
         
     }
}
print_r($permission_categories);
exit();

Hope this is what you expect.
Happy coding .. :)

<?php
$permissions = ['create_user', 'create_post','edit_post', 'delete_post', 'edit_user', 'delete_user'];
$permission_categories = [];
$set = [];
        
foreach ($permissions as $permission) {
   $name = explode("_", $permission);
   $key = $name[1];
   $value = $name[0];

    if (!array_key_exists($key, $permission_categories)) {
        $permission_categories[$key] = [$value];
    }else{
         array_push($permission_categories[$key],$value);
         
     }
}
print_r($permission_categories);
exit();