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<?php $c = " total used free shared buffers cached\nMem: 494 383 111 0 29 200\n-/+ buffers/cache: 153 341\nSwap: 255 0 255"; preg_match("/Mem:\s+(?P<total>\d+)/", $c ,$r); print_r($r);
Output for 4.3.3 - 4.3.11, 4.4.0 - 4.4.9, 5.0.0 - 5.0.5, 5.1.0 - 5.1.6, 5.2.0 - 5.2.17, 5.3.0 - 5.3.29, 5.4.0 - 5.4.45, 5.5.0 - 5.5.38, 5.6.0 - 5.6.40, 7.0.0 - 7.0.33, 7.1.0 - 7.1.33, 7.2.0 - 7.2.33, 7.3.0 - 7.3.33, 7.4.0 - 7.4.33, 8.0.0 - 8.0.30, 8.1.0 - 8.1.27, 8.2.0 - 8.2.17, 8.3.0 - 8.3.4
Array ( [0] => Mem: 494 [total] => 494 [1] => 494 )
Output for 4.3.0 - 4.3.2
Array ( [0] => Mem: 494 [1] => 494 )

preferences:
284.21 ms | 401 KiB | 456 Q