如何获得第一个数组元素本身？

I have an array of data which is :

Array
(
[0] => Array
    (
        [chat_categories] => one cat
        [display_name] => admin user
        [user_email] => testemail1@email.com
        [user_login] => user
    )

[1] => Array
    (
        [chat_categories] => one cat
        [display_name] => Test User
        [user_email] => testemail@testsite.com
        [user_login] => testuser
    )

)

Now I want to get the first element from that array, check if the values display_name, user_email and user_login matches and update chat_categories column in a wordpress user table if matched successfully.

so, in my case, this helped me,

   for($i=0; $i<sizeof($arr); $i++){
    $data = $arr[$i];
    $chat_categories = $data[chat_categories];
    $display_name = $data[display_name];
    $user_email = $data[user_email];
    $user_login = $data[user_login];
    $success = $wpdb->query("UPDATE $userTableName SET chat_categories = '$chat_categories' WHERE user_email = '$user_email' AND user_login ='$user_login' ");
    }   

You can also use foreach loop as:

$arr = array(
            "0" => array(
                   "chat_categories" => "one cat",
                   "display_name" => "admin user",
                   "user_email" => "testemail1@email.com",
                   "user_login" => "user"
             ),
           "1" => array(
                  "chat_categories" => "one cat",
                  "display_name" => "Test User",
                  "user_email" => "testemail@testsite.com",
                  "user_login" => "testuser"
            )
   );

foreach($arr as $innerArr){    
    $chat_categories = $innerArr["chat_categories"];
    $display_name = $innerArr["display_name"];
    $user_email = $innerArr["user_email"];
    $user_login = $innerArr["user_login"];
    $success = $wpdb->query("UPDATE $userTableName SET chat_categories = '".$chat_categories."' WHERE user_email = '".$user_email."' AND user_login ='".$user_login."'");
    }