php - How to remove the first element of array without changing its key value?

I have an array in php

$array=array("a"=>"123","b"=>"234","c"=>"345");
array_shift($array);
//array("0"=>"234","1"=>"345");
?>

If I use this function, then key value gets changed. I want my key value to remain the same. How can I remove first element without affecting array key values.
My answer should be like

array("b"=>"234","c"=>"345");

Note:Please do not use foreach(); I want to do this by existing array functions in php

array_splice function is working for above array. But consider the below array

$array = Array

(
    '39' => Array
        (
            'id' => '39',
            'field_id' => '620'

        ),

    '40' => Array
        (

            'id' => '40',
            'field_id' => '620',
            'default_value' => 'rrr',

));

array_splice($array, 0, 1);
print_r($array);
?>

It is showing answer as follows:

Array ( [0] => Array ( [id] => 40 [field_id] => 620 [default_value] => rrr ) )

May I know the reason?? Will array_splice() work only for single dimensional array?? Now key value is reset...

Answer

In case you do not know what the first item's key is:

// Make sure to reset the array's current index
reset($array);

$key = key($array);
unset($array[$key]);