php 连接数据库解决思路

php 连接数据库
出错为：

Warning: mysql_fetch_assoc(): supplied argument is not a valid MySQL result resource in E:\phpser\AppServ\www\mzgz1.php on line 115
JpGraph Error: HTTP headers have already been sent.
Caused by output from file mzgz1.php at line 115. 
Explanation:
HTTP headers have already been sent back to the browser indicating the data as text before the library got a chance to send it's image HTTP header to this browser. This makes it impossible for the library to send back image data to the browser (since that would be interpretated as text by the browser and show up as junk text).
Most likely you have some text in your script before the call to Graph::Stroke(). If this texts gets sent back to the browser the browser will assume that all data is plain text. Look for any text, even spaces and newlines, that might have been sent back to the browser. 

For example it is a common mistake to leave a blank line before the opening " 

代码为：
ini_set('date.timezone','Asia/Shanghai'); // 'Asia/Shanghai' 为上海时区 
$day=date("Y-m-d");     //获取当前日期
$timer=date("H:00:00");//获取当前的时间
$yestday=date("Y-m-d",strtotime("-1 day"));//获取昨天时间
$conn=mysql_connect('localhost','root','root');
mysql_select_db("pm25",$conn);
mysql_query("set names utf8");
$arr=mysql_query("select pm25,time from ceshi where data='$day'",$conn);   //查询日期为今天结果赋值给数组arr
$arr1=mysql_query("select pm25,time from ceshi where data=$yestday",$conn);   //查询日期为昨天结果赋值给数组arr1
$time=array(
"0"=>"00:00:00",
"1"=>"01:00:00",
"2"=>"02:00:00",
"3"=>"03:00:00",
"4"=>"04:00:00",
"5"=>"05:00:00",
"6"=>"06:00:00",
"7"=>"07:00:00",
"8"=>"08:00:00",
"9"=>"09:00:00",
"10"=>"10:00:00",
"11"=>"11:00:00",
"12"=>"12:00:00",
"13"=>"13:00:00",
"14"=>"14:00:00",
"15"=>"15:00:00",
"16"=>"16:00:00",
"17"=>"17:00:00",
"18"=>"18:00:00",
"19"=>"19:00:00",
"20"=>"20:00:00",
"21"=>"21:00:00",
"22"=>"22:00:00",
"23"=>"23:00:00"
);
$pm25=array("0","0","0","0","0","0","0","0","0","0","0","0","0","0","0","0","0","0","0","0","0","0","0","0");
$pm25today=array("0","0","0","0","0","0","0","0","0","0","0","0","0","0","0","0","0","0","0","0","0","0","0","0");
$pm25yestday=array("0","0","0","0","0","0","0","0","0","0","0","0","0","0","0","0","0","0","0","0","0","0","0","0");
while($result=mysql_fetch_assoc($arr)){
//echo "yes2";
for($j=0;$j //echo "yes1";
if ($result['time']==$time[$j]){
$pm25today[$j]=$result['pm25']; //存放今天的Pm2.5
//echo "yes";
}
}
}
while($result=mysql_fetch_assoc($arr1)){
//echo "yes2";
for($j=0;$j //echo "yes1";
if ($result['time']==$time[$j]){
$pm25yestday[$j]=$result['pm25']; //存放昨天的Pm2.5
//echo "yes";
}
}
}
for($i=0;$i if ($pm25[$i]==0){
  $pm25today[$i]= $pm25today[$i-1]; //获取今天PM25数据
}
}
$a1=array("0点","1点","2点","3点","4点","5点","6点","7点","8点","9点","10点","11点","12点","13点","14点","15点","16点","17点","18点","19点","20点","21点","22点","23点"); //设置X轴
$a=array("0点","1点","2点","3点","4点","5点","6点","7点","8点","9点","10点","11点","12点","13点","14点","15点","16点","17点","18点","19点","20点","21点","22点","23点"); //设置X轴
if($timer=="23:00:00"){
$pm25[$i]=$pm25today[$i];
if($pm25[0]==0){
$arr=NULL;
$daytimer=0;
while($arr==NULL){
$daytimer++;
$day=date("Y-m-d",strtotime("-$daytimer day"));
$arr=mysql_query("select pm25 from ceshi where data=$day",$conn);
}
$a3=mysql_num_rows($arr);
$result=mysql_fetch_assoc($arr[$a3]); //去最后一条记录
$pm25[0]=$result['pm25'];
}
}
else{ //初始化
$m=0;
$yestimer=date("H:00:00",strtotime("+1 hour"));//24小时之前的时间
for($j=0;$j if($timer==$time[$j]){
$m=$j;//标记现在时间位置
}
}
for($i=0;$i if ($pm25[$i]==0){
  $pm25yestday[$i]= $pm25yesday[$i-1]; //获取昨天PM25数据
}
}
$m1=23-$m;
$m2=23-$m;
for($j=0;$j $pm25[$j]=$pm25yestday[24-$m1];
$m1=$m1+1;
}
for($i=0;$i $pm25[$m2]=$pm25today[$i];
$m2++;
}

if($pm25[0]==0){
$arr=NULL;
$daytime=3;
while($arr==NULL){
$day3=date("Y-m-d",strtotime("-$daytime day"));
$arr=mysql_query("select pm25 from ceshi where data=$day3",$conn);
$daytime++;
}
$a4=mysql_num_rows($arr);
$result=mysql_fetch_assoc($arr[$a4]); //去最后一条记录
$pm25[0]=$result['pm25'];
}

for($j=23-$m;$j $m1=$j-$m;
$a[$j]=$a1[$m1];
}
for($j=0;$j $a[$j]=$a1[$n];
$n=$n+1;
}
}
 //用PHP画折线图
  include("E:/phpser/AppServ/jpgraph/jpgraph/jpgraph.php");
  include("E:/phpser/AppServ/jpgraph/jpgraph/jpgraph_line.php");
//$datay = array(109,120,120,97,112,135,135,106,106,106,204,124,124,124,119,109,118,118,197,155,142,142,136,137); //填充的数据
$datay=$pm25;
  $graph = new Graph(700,300,"auto");    //生成画布
  $graph->img->SetMargin(50,40,30,40);  //设置画布的边距
  $graph->img->SetAntiAliasing();     //设置拆线的平滑状态
  $graph->SetScale("textlin");     //设置刻度样式
  $graph->SetShadow();//创建画布阴影
  $graph->title->Set("最近24小时pm2.5值的变化");//设置标题
  $graph->title->SetFont(FF_SIMSUN,FS_BOLD);//设置标题字体
  $graph->SetMarginColor("lightblue");//设置画布的背景颜色为淡蓝色
  $graph->yaxis->title->SetFont(FF_SIMSUN,FS_BOLD);//设置Y轴标题的字体
  $graph->xaxis->SetPos("min");
  $graph->yaxis->HideZeroLabel();
  $graph->ygrid->SetFill(true,[email protected]',[email protected]');
  //$a=array("0点","1点","2点","3点","4点","5点","6点","7点","8点","9点","10点","11点","12点","13点","14点","15点","16点","17点","18点","19点","20点","21点","22点","23点"); //设置X轴
  $graph->xaxis->SetTickLabels($a);
  $graph->xaxis->SetFont(FF_SIMSUN);   //设置X坐标轴的字体
  $graph->yscale->SetGrace(20);
  $p1 = new LinePlot($datay);    //创建折线图对象
  $p1->mark->SetType(MARK_FILLEDCIRCLE);    //设置数据坐标点为图形标记
  $p1->mark->SetFillColor("red");     //设置填充的颜色
  $p1->mark->SetWidth(4); //设置圆柱形标记的直径为4像素
  $p1->mark->SetColor("blue");    //设置拆线颜色为蓝色
  $p1->SetCenter();   //在X轴的各坐标点中心位置绘制拆线
  $graph->Add($p1);    //在统计图上绘制折线
  $graph->Stroke();   //输出图像
?>
------解决思路----------------------
115行是哪行？