Your implode and array_map function are wrong.

Also, your code has rounding problems as description does not mention of doing so.

Instead, you should follow this:

With Golang (and maybe others) you can use a format with "%.0f" for "Buy" and "Sell".

Be very carefull with eval. Basically you should not do it. And if you do - sanitize input.

lol

why to traverse through array twice, so this solution will reduce the number of operations in half.

Empty array will result division by zero.