How to slice an array by key, not offset?

To find the offset of the key, use array_search() to search through the keys, which can be retrieved with array_keys(). array_search() will return FALSE when the specified key (100) is not present in the array ($a).

$key = array_search(100, array_keys($a), true);if ($key !== false) {    $slice = array_slice($a, $key, null, true);    var_export($slice);}

Prints:

array (  100 => 'aa',  101 => 'bb',  102 => 'cc',)

Returns parts of $array whose keys exist in the array $keys:

array_intersect_key($array,array_flip($keys));

Alternative solution

If you want to slice the array by using keys for the items you want to get, you could use the following custom function to do so:

function array_slice_keys($array, $keys = null) {    if ( empty($keys) ) {        $keys = array_keys($array);    }    if ( !is_array($keys) ) {        $keys = array($keys);    }    if ( !is_array($array) ) {        return array();    } else {        return array_intersect_key($array, array_fill_keys($keys, '1'));    }}

Usage:

$ar = [    'key1' => 'a',    'key2' => 'b',    'key3' => 'c',    'key4' => 'd',    'key5' => 'e',    'key6' => 'f',];// Get the values from the array with these keys:$items = array_slice_keys( $ar, array('key2', 'key3', 'key5') );

Result:

Array(    [key2] => b    [key3] => c    [key5] => e)