An excel spreadsheet will add characters to the file you won't want to deal with. You are better off going with a plain text file and a delimiter. For example, as suggested above, tab-delimited:
UserName\tPassword\tOther Information
Or Comma-Delimited (CSV):
UserName,Password,Other Information,More Information
With PHP you can use the explode(delimiter, text) to get the values in to an array for use.
Above the "\t" character is just an abbreviation for tab and also the character you would use in explode when specifing the delimiter. You can look up the explode function on php.net if you need more information about how it works but it does a great job for delimited file.
The only thing to remember is if you're going to use explode you have to make sure your delimiter is not placed in the file (ie. no commas if you're using CSV or no tabs if you're using tab-delimited) other then for actual delimiter. If they are present explode will work in a way you did not expect.