php實現二分查找算法

// $low and $high have to be integers

function BinarySearch( $array, $key, $low, $high )
{
    if( $low > $high ) // termination case
    {
        return -1;
    }

$middle = intval( ( $low+$high )/2 ); // gets the middle of the array

if ( $array[$middle] == $key ) // if the middle is our key
{
    return $middle;
}
elseif ( $key < $array[$middle] ) // our key might be in the left sub-array
{
    return BinarySearch( $array, $key, $low, $middle-1 );
}  

return BinarySearch( $array, $key, $middle+1, $high ); // our key might be in the right sub-array

}</pre>