[Ghosted]

public CheckData(id) {
	
	if(g_PlayerXP[id] < 0) {
		
		g_PlayerXP[id] = 0
	}
	
	if(g_PlayerXP[id] < 100) { 
		g_PlayerLevel[id] = 0
	}
	
	if(g_PlayerXP[id] >= 100 && g_PlayerXP[id] < 200) { 
		g_PlayerLevel[id] = 1
	}
	
	if(g_PlayerXP[id] >= 200 && g_PlayerXP[id] < 300) { 
		g_PlayerLevel[id] = 2 
	}
	
	if(g_PlayerXP[id] >= 300 && g_PlayerXP[id] < 400) { 
		g_PlayerLevel[id] = 3 
	}
	
	if(g_PlayerXP[id] >= 400 && g_PlayerXP[id] < 500) { 
		g_PlayerLevel[id] = 4 
	}
	
	if(g_PlayerXP[id] >= 500 && g_PlayerXP[id] < 600) {
		g_PlayerLevel[id] = 5
	}
	
	if(g_PlayerXP[id] >= 600 && g_PlayerXP[id] < 700) { 
		g_PlayerLevel[id] = 6
	}
	
	if(g_PlayerXP[id] >= 700 && g_PlayerXP[id] < 800) {
		g_PlayerLevel[id] = 7
	}
	if(g_PlayerXP[id] >= 800 && g_PlayerXP[id] < 900) { 
		g_PlayerLevel[id] = 8
	}
	
	if(g_PlayerXP[id] >= 900 && g_PlayerXP[id] < 1000) {
		g_PlayerLevel[id] = 9
	}
	
	if(g_PlayerXP[id] >= 1000 && g_PlayerXP[id] < 1100) { 
		g_PlayerLevel[id] = 11
	}
	
	if(g_PlayerXP[id] >= 1100 && g_PlayerXP[id] < 1200) { 
		g_PlayerLevel[id] = 12
	}
	
	if(g_PlayerXP[id] >= 1200 && g_PlayerXP[id] < 1300) { 
		g_PlayerLevel[id] = 13
	}
	
	if(g_PlayerXP[id] >= 1300 && g_PlayerXP[id] < 1400) { 
		g_PlayerLevel[id] = 14
	}
	
	if(g_PlayerXP[id] >= 1400) { 
		g_PlayerLevel[id] = 15
	}	
	
}

OMG!
Add g_PlayerReqXP (required xp for next level and change this CheckData to:

public CheckData(id) {
	
	if(g_PlayerXP[id] >= g_PlayerReqXP[id])
        {
		g_PlayerXP[id] -= g_PlayerReqXP[id];
                g_PlayerReqXP[id] += 100;
                g_PlayerLevel[id]++;
	}
	
}

OR:

public CheckData(id) {
	
	
	if(g_PlayerXP[id] >= g_PlayerLevel[id] * 100) // minimum player lvl = 1
        {
		g_PlayerXP[id] -= (g_PlayerLevel[id] * 100);
                g_PlayerLevel[id]++;
	}
	
}