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<?php $postcodes = ['SO30 0NG', 'SO30 OTD', 'SO31 1TG', 'RG51 5HG', 'RG51 7GH']; $result= array(); Foreach ($postcodes as $postcode){ $short =Substr($postcode,0,4); If(!isset($result[$short])) $result[$short]=[]; $result[$short][]= $short; } Var_dump($result);
Output for 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 - 8.1.33, 8.2.0 - 8.2.29, 8.3.0 - 8.3.26, 8.4.1 - 8.4.13
array(3) { ["SO30"]=> array(2) { [0]=> string(4) "SO30" [1]=> string(4) "SO30" } ["SO31"]=> array(1) { [0]=> string(4) "SO31" } ["RG51"]=> array(2) { [0]=> string(4) "RG51" [1]=> string(4) "RG51" } }
preferences:
151.22 ms | 409 KiB | 5 Q