FPS camera

im trying to get a “camera” working so that it can go through my 3d level ive got it to compile with no issues but the camera doesnt move at all when i press a key, can anyone see where ive gone wrong

void keyboard (unsigned char key, int x, int y) {
    if (key=='q')
    {
    xrot += 1;
    if (xrot >360) xrot -= 360;
    }

    if (key=='z')
    {
    xrot -= 1;
    if (xrot < -360) xrot += 360;
    }

    if (key=='w')
    {
    float xrotrad, yrotrad;
    yrotrad = (yrot / 180 * 3.141592654f);
    xrotrad = (xrot / 180 * 3.141592654f);
    xpos += float(sin(yrotrad)) ;
    zpos -= float(cos(yrotrad)) ;
    ypos -= float(sin(xrotrad)) ;
    }

    if (key=='s')
    {
    float xrotrad, yrotrad;
    yrotrad = (yrot / 180 * 3.141592654f);
    xrotrad = (xrot / 180 * 3.141592654f);
    xpos -= float(sin(yrotrad));
    zpos += float(cos(yrotrad)) ;
    ypos += float(sin(xrotrad));
    }

    if (key=='d')
    {
    yrot += 1;
    if (yrot >360) yrot -= 360;
    }

    if (key=='a')
    {
    yrot -= 1;
    if (yrot < -360)yrot += 360;
    }
    if (key==27)
    {
    exit(0);
    }
}

void mouseMovement(int x, int y) {
    int diffx=x-lastx; 
    int diffy=y-lasty; 
    lastx=x; 
    lasty=y; 
    xrot += (float) diffy; 
    yrot += (float) diffx; 
 
}

How do you tell OpenGL to use those values for the camera?