Help getting 'Keys' out of multi-dimensional array
Could anyone advise me on the most simple and efficient way of getting 'keys' out of a multi-dimensional array.
I have the multi-dimensional Array :
This array stores the relationships between $C , $L & $P as Keys, which I then want to use in individual queries. Rather than having to use 3 loops to get the inforamtion (I want to get all the keys for each sub-array) is there not an easier more efficient function I could use ?? I tried the below but it through out errors as I can't use  for reading.
$C_QUERY_ids = array_keys($C_L_P_CurrentPage);
$L_QUERY_ids = array_keys($C_L_P_CurrentPage);
$P_QUERY_ids = array_keys($C_L_P_CurrentPage););