Your objective is to create an api script using php which does the following:
1. download keyword report for time frame 'yesterday' from adwords
2. for each keyword, compare cost per conversion from report to target cpl (15.00 eur).
3. if cost per conversion < target cpl, increase bid by 3%, if cost per conversion > target cpl, decrease bid by 5%
all bids on keyword level.
The task needs to be done via api, no google scripts or automatic rules.
Please let me now approximate time you would need for that.