IOS OpenGL ES - Rotate Camera around the scene - opengl-es

Question

This is my code:
- (void)drawView {
// Define square for flowers head (vertecies)
const GLfloat flowerHead[] = {
-1.0, 1.0, 1.0, // top left
-1.0, -1.0, 1.0, // bottom left
1.0, -1.0, 1.0, // bottom right
1.0, 1.0, 1.0
};
// Define the texture coordinates --> as the flowerHead vertecies
const GLshort flowerHeadTextureCoord[] = {
0, 1, // top left
0, 0, // bottom left
1, 0, // bottom right
1, 1 // top right
};
rota = 1.0;
[EAGLContext setCurrentContext:context];
glBindFramebufferOES(GL_FRAMEBUFFER_OES, viewFramebuffer);
glViewport(0, 0, backingWidth, backingHeight);
glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
glMatrixMode(GL_MODELVIEW);
glTexCoordPointer(2, GL_SHORT, 0, flowerHeadTextureCoord);
glEnableClientState(GL_TEXTURE_COORD_ARRAY);
// flower #1
glPushMatrix();
{
glEnable(GL_ALPHA_TEST); // enable alpha -> transparency state
glTranslatef(0.0, 0.0, -6.0); // positioning the flower
glRotatef(55.0, 1.0, 0.0, 0.0); // rotate flower on (x) axis
glVertexPointer(3, GL_FLOAT, 0, flowerHead); // pointer to the flowerHead vertecies array
glEnableClientState(GL_VERTEX_ARRAY); // enable the vertex array state
// Draw the front face
// Bind texture
glBindTexture(GL_TEXTURE_2D, textures[0]);
glDrawArrays(GL_TRIANGLE_FAN, 0, 4);
}
glPopMatrix();
glBindRenderbufferOES(GL_RENDERBUFFER_OES, viewRenderbuffer);
[context presentRenderbuffer:GL_RENDERBUFFER_OES];
[self checkGLError:NO];
}
Now this is my drawing code...all I need now is to rotate the camera around the object (and not the object itself)...
My setupView function:
const GLfloat zNear = 0.1, zFar = 1000.0, fieldOfView = 60.0;
GLfloat size;
// Set the general polygon properties - for transparency!!!
glBlendFunc(GL_SRC_ALPHA,GL_ONE_MINUS_SRC_ALPHA);
glAlphaFunc(GL_GREATER,0.1f);
glEnable(GL_DEPTH_TEST);
glMatrixMode(GL_PROJECTION);
size = zNear * tanf(DEGREES_TO_RADIANS(fieldOfView) / 2.0);
// This give us the size of the iPhone display
CGRect rect = self.bounds;
glFrustumf(-size, size, -size / (rect.size.width / rect.size.height), size / (rect.size.width / rect.size.height), zNear, zFar);
glViewport(0, 0, rect.size.width, rect.size.height);
glClearColor(0.0f, 0.0f, 0.0f, 0.5f);