i have a problem where whenever u move the camera all the object on screen disappear here is my code

class camera
{
    public:
        GLfloat eye[3];
        GLfloat up[3];
        GLfloat side[3];
        GLfloat look[3];
        GLfloat matrix[3][3];
        GLfloat vertMatrix[3];
        GLfloat tmpMatrix[3];
        camera()
        { // Camera Position
            eye[0] = 0.0f;  eye[1] = 0.0f;  eye[2] =  0.0f;
            up[0] = 0.0f;   up[1] = 1.0f;   up[2] =  0.0f;
            side[0] = 1.0f; side[1] = 0.0f; side[2] =  0.0f;
            look[0] = 0.0f; look[1] = 0.0f; look[2] = -1.0f;
            matrix = {
            {side[0] - eye[0], up[0] - eye[0], look[0] - eye[0]},
            {side[1] - eye[1], up[1] - eye[1], look[1] - eye[1]},
            {side[2] - eye[2], up[2] - eye[2], look[2] - eye[2]}};
        };
        void updatePosi()
        {
            glLoadIdentity();// Update the camera
            gluLookAt( eye[0], eye[1], eye[2], look[0], look[1], look[2], up[0] - eye[0], up[1] - eye[1], up[2] - eye[2]);
        }
        void translatePosi(GLfloat x1, GLfloat y1, GLfloat z1)
        {
            matrix = {
            {side[0] - eye[0], up[0] - eye[0], look[0] - eye[0]},
            {side[1] - eye[1], up[1] - eye[1], look[1] - eye[1]},
            {side[2] - eye[2], up[2] - eye[2], look[2] - eye[2]}
            };
            vertMatrix = { x1, y1, -z1};
            tmpMatrix =  {matrix[0][0] * vertMatrix[0] + matrix[0][1]* vertMatrix[0] + matrix[0][2]* vertMatrix[0],
            matrix[1][0] * vertMatrix[1] + matrix[1][1]* vertMatrix[1] + matrix[1][2]* vertMatrix[1],
            matrix[2][0] * vertMatrix[2] + matrix[2][1]* vertMatrix[2] + matrix[2][2]* vertMatrix[2]};
            eye[0] += tmpMatrix[0];  eye[1] += tmpMatrix[1];  eye[2] +=  tmpMatrix[2];
            up[0] += tmpMatrix[0];   up[1] += tmpMatrix[1];   up[2] +=  tmpMatrix[2];
            side[0] += tmpMatrix[0]; side[1] += tmpMatrix[1]; side[2] +=  tmpMatrix[2];
            look[0] += tmpMatrix[0]; look[1] += tmpMatrix[1]; look[2] += tmpMatrix[2];
        }
};

void display()
{
    glClearColor( 0.0, 0.0f, 0.0, 1.0f);
    glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
    keymanage();
    glLoadIdentity();
    cam.updatePosi();
    enable();
    glutSolidCube(0.25f);
    glutSwapBuffers();
}

int main(int argc, char **args)
{
    glutInit(&argc, args);
    glutInitDisplayMode(GLUT_RGBA | GLUT_DOUBLE | GLUT_DEPTH);
    glutInitWindowSize(500, 500);
    glutInitWindowPosition(100, 100);
    glutCreateWindow("opengl mycode");
    init();
    glutDisplayFunc(display);
    glutIdleFunc(display);
    glutReshapeFunc(reshape);
    glutKeyboardFunc(keyDown);
    glutKeyboardUpFunc(keyUp);
    glutMainLoop();
    return 0;
}

i 'm am very new to opengl so any help would be appreciated.

Are you perhaps incrementing the camera position on key presses?
Remember that you are incrementing the camera by that value every frame, so it could be that your camera moves so fast that the objects appear to disappear instantly.

If so, try using very small values for the translation function and see if it works.

EDIT: Also like Geometrian said, your matrix stuff is overly complicated. And you should keep your lookAt up vector at (0.0, 1.0, 0.0).