<?php
$json = <<<JSON
[ [ 51.11041991029261, -2.274169921875 ], [ 51.08282186160978, -3.460693359375 ], [ 50.443513052458044, -3.570556640625 ], [ 50.443513052458044, -1.966552734375 ] ]
JSON;
$coords = json_decode($json, true);
$lats = array_map(function (array $coord) { return $coord[0]; }, $coords);
$lons = array_map(function (array $coord) { return $coord[1]; }, $coords);
var_dump($lats, $lons);
preferences:
40.59 ms | 402 KiB | 5 Q