PHP get previous array element knowing current array key

Question

I have an array with specific keys:

array(
    420 => array(...), 
    430 => array(...), 
    555 => array(...)
)

In my applicati

Answer 1

Expanding further on the solution of Luca Borrione and cenk, so that you can wrap around the end of the array in either direction, you may use:

function getAdjascentKey($key, $hash = array(), $increment) {
    $keys = array_keys($hash);    
    $found_index = array_search($key, $keys);
    if ($found_index === min(array_keys($keys)) && $increment === -1) {
        $found_index = max(array_keys($keys))+1;
    }
    if ($found_index === max(array_keys($keys)) && $increment === +1) {
        $found_index = min(array_keys($keys))-1;
    }       
    return $keys[$found_index+$increment];
}