PHP version of verification code program_PHP tutorial

//Generate verification code image
Header("Content-type: image/PNG");
srand((double)microtime()*1000000);//Sow a seed to generate random numbers to facilitate the use of random number generation below

session_start();//Save random numbers into session
$_SESSION['authnum']="";
$im = imagecreate(62,20); //Specify the image background size

$black = ImageColorAllocate($im, 0,0,0); //Set three colors
$white = ImageColorAllocate($im, 255,255,255);
$gray = ImageColorAllocate($im, 200,200,200);

imagefill($im,0,0,$gray); //Adopt area filling method, set (0,0)

while(($authnum=rand() 0000)<10000);
//Draw the four-digit integer verification code into the picture
$_SESSION['authnum']=$authnum;
imagestring($im, 5, 10, 3, $authnum, $black);
// Use col color to draw the string s to the x, y coordinates of the image represented by image (the upper left corner of the image is 0, 0).
//If font is 1, 2, 3, 4 or 5, use the built-in font

for($i=0;$i<200;$i ) //Add interference pixels
{
$randcolor = ImageColorallocate($im,rand(0,255),rand(0,255),rand(0,255));
imagesetpixel($im, rand()p , rand()0 , $randcolor);
}


ImagePNG($im);
ImageDestroy($im);
?>

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