PHP implements binary search algorithm

// $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
}

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