Add a string to each date in an array

Add a string to each date in an array

This is a simple questions. I do not know i'm not able to achieve this.
How to add a string(Date.UTC) to each date in the row using php like show
below
[Date.UTC(2011,11,20),5],[Date.UTC(2011,11,21),5]
As of now i have my result like this, just need to add Date.UTC string to
each date in the row.
[["2011,09,03","1"],["2011,09,06","53"]]