C++ :: Convert Int Array To String

I'm trying to convert int x and y arrays to string using a sample code found online.

string Square::int2string (int x[]) {
string returnstring = "";
for (int i=0; i < 4; i++) {
returnstring += itoa(x[i]);
return returnstring;
}
}

but hit with the following error.

Square.cpp:30:8: error: prototype for ‘std::string Square::int2string(int*)’ does not match any in class ‘Square’ Square.h:21:10: error: candidate is: std::string Square::int2string()

I declared the following in header file.

string int2string();

The error is due to variable type does not match. Is there a better way to convert int array to string?

What I'm trying to achieve is a string printed in the following manner:

Point[0] (x1,y1)
Point[1] (x2,y2) and so on.