Строка: 
[27/Apr/2020:19:14:17 +0000] GET https://domain/api/lead/0/43927/0/0 pid:28254 took:0.171s mem:8mb cpu:58.62% status:200 {54.227.122.223|Zapier}
Регулярка: 
$regex = '/(^\[(?<datetime>.*)\]) (?P<method>OPTIONS|GET|HEAD|POST|PUT|DELETE|TRACE|CONNECT|PATCH|PROPFIND) (?P<url>.+?\S) (?P<pid>.+?\S) (?P<took>.+?\S) (?P<mem>.+?\S) (?P<cpu>.+?\S) (?P<status>.+?\S+)/';
Результат:
Array
(
    [0] => [27/Apr/2020:19:14:17 +0000] GET https://domain/api/lead/0/43927/0/0 pid:28254 took:0.171s mem:8mb cpu:58.62% status:200
    [1] => [27/Apr/2020:19:14:17 +0000]
    [datetime] => 27/Apr/2020:19:14:17 +0000
    [2] => 27/Apr/2020:19:14:17 +0000
    [method] => GET
    [3] => GET
    [url] => https://domain/api/lead/0/43927/0/0
    [4] => https://domain/api/lead/0/43927/0/0
    [pid] => pid:28254
    [5] => pid:28254
    [took] => took:0.171s
    [6] => took:0.171s
    [mem] => mem:8mb
    [7] => mem:8mb
    [cpu] => cpu:58.62%
    [8] => cpu:58.62%
    [status] => status:200
    [9] => status:200
)
Как в  pid, took, mem, cpu, status получить только цифровые значения? 
Что бы было к примеру 
['pid' => 28254, 'cpu' => 58.62]