Get only the array elements with certain keys [duplicate]

Answer 1

First you need to get an array containing the keys. array_keys

Then, you need to filter the keys to find the ones you want. array_filter

Use this callback:

function($a) {return substr($a,0,8) == "special_";}

Then flip the array so that the keys are keys again instead of values. array_flip

Finally, intersect those keys with the original array. array_intersect_key

Result:

$special_items = array_intersect_key($items,array_flip(array_filter(array_keys($items),function($a) {return substr($a,0,8) == "special_";})));