How can i transform these number into the ones below:

£6500000
£3900000

£6.50m
£3.90m

The number_format function would be the best for general number, but the money_format could be what you want.

http://uk.php.net/manual/en/function.number-format.php
http://uk.php.net/manual/en/function.money-format.php

You could also divide by 6 and then put £{$number}m but it's up to you

how would diving by 6 help?

I think he means divide by 1000000 and round....