Search array keys and return the index of matched key

[Zoey_Michigan]

my array looks like this:\[code\][sx1] => Array ( [sx1] => Pain in Hand [sx1L] => Location [sx1O] => Other Treat [sx1T] => Type [sx1R] => Radiation [sx1A] => Aggrivate Ease [sx1D] => Duration [sx1I] => Irit [sx1P] => Previous Hx [SX1T_1] => CX [SX1T_2] => Shld [SX1T_3] => Trnk [SX1T_4] => Hip [SX1T_5] => )\[/code\]I need to be able to search the array by a key, and then return the index of the matched item.For example, I need to search the array for the key "SX1T_1" and then return the index of that item in the array.Thanks for any help.