PHP数组索引未定义，虽然它存在

Question

Given an array as follow :

$z = [
 "cat lovers" => [
     "name" => "cat lovers",
     "impressions" => 2038,
     "ctr" => 0.032875368007851,
     "actions" => [
       [
         "action_type" => "attention_event",
         "value" => "232",
       ],
       [
         "action_type" => "landing_page_view",
         "value" => "18",
       ],
     ],
 "shorty kodi" => [
     "name" => "shorty kodi",
     "impressions" => 534,
     "ctr" => 0.041198501872659,
     "actions" => [
       [
         "action_type" => "attention_event",
         "value" => "56",
       ],
       [
         "action_type" => "landing_page_view",
         "value" => "7",
       ]
     ]
]

Following code run with no error :

foreach($z as $i) {
    print_r(array_column($i["actions"], "action_type"));
}

But if we remove the print_r function to like :

foreach($z as $i) {
   $b = array_column($i["actions"], "action_type");
}

It results an error saying :

PHP error:  Undefined index: actions on line 2

Any idea why?

Thanks

Answer 1

It's working fine, I just checked it. put print_r($b); inside or after foreach. You will get the same result as you're getting from the first foreach.