Why can't I output a picture

Why can't I output a picture

Session_Start ();

Number of random codes
$_rnd_code = 4;

Create Random Code
for ($i =0; $i <4; $i + +) {
$_nmsg.=dechex (Mt_rand (0,15));
}

Save session
$_session[' Code ']=$_nmsg;

Long and high
$_width = 75;
$_height = 25;

Create an image
$_img = Imagecreatetruecolor ($_width,$_height);



Output image
Header (' content-type:image/png ');
Imagepng ($_IMG);

The output result is

Notice: Undefined variable: _rnd_code inD:\AMP\web\ide_tmp.phpOn line -



Warning: Division by zero inD:\AMP\web\ide_tmp.phpOn line -



Notice: Undefined variable: _heght inD:\AMP\web\ide_tmp.phpOn line -



Warning: Mt_rand (): Max (0) is smaller than min (1) inD:\AMP\web\ide_tmp.phpOn line -



Notice: Undefined variable: _rnd_code inD:\AMP\web\ide_tmp.phpOn line -



Warning: Division by zero inD:\AMP\web\ide_tmp.phpOn line -



Notice: Undefined variable: _heght inD:\AMP\web\ide_tmp.phpOn line -



Warning: Mt_rand (): Max (0) is smaller than min (1) inD:\AMP\web\ide_tmp.phpOn line -



Notice: Undefined variable: _rnd_code inD:\AMP\web\ide_tmp.phpOn line -



Warning: Division by zero inD:\AMP\web\ide_tmp.phpOn line -



Notice: Undefined variable: _heght inD:\AMP\web\ide_tmp.phpOn line -



Warning: Mt_rand (): Max (0) is smaller than min (1) inD:\AMP\web\ide_tmp.phpOn line -



Notice: Undefined variable: _rnd_code inD:\AMP\web\ide_tmp.phpOn line -



Warning: Division by zero inD:\AMP\web\ide_tmp.phpOn line -



Notice: Undefined variable: _heght inD:\AMP\web\ide_tmp.phpOn line -



Warning: Mt_rand (): Max (0) is smaller than min (1) inD:\AMP\web\ide_tmp.phpOn line -



Notice: Undefined variable: _rnd_code inD:\AMP\web\ide_tmp.phpOn line -



Warning: Division by zero inD:\AMP\web\ide_tmp.phpOn line -



Notice: Undefined variable: _heght inD:\AMP\web\ide_tmp.phpOn line -



Warning: Mt_rand (): Max (0) is smaller than min (1) inD:\AMP\web\ide_tmp.phpOn line -

‰png

Modify by error message
Then you have to:
Still unfriendly "captcha" picture
Comment out the header and open the error to see the error.

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