Solution to 'The image cannot be displayed because of its own errors' when PHP generates verification code_PHP Tutorial

Today I used code to implement the PHP verification code generation function. I found that Firefox kept prompting "The image...cannot be displayed because of its own errors." The author also reminded that "If the browser displays "Image

So I googled deeply and most of the solutions were to delete all the spaces and press Enter before the code "

Confirmation code generation file checkNum_session.php

Copy code The code is as follows:

Header( "Content-type: image/png");
/*
* Initialization
*/
$border = 1; //Whether you want a border 1 Yes: 0 No
$how = 4; //Verification code digits
$w = $how*15; //Picture width
$h = 20; //Picture height
$fontsize = 6; //Font size
$alpha = "abcdefghijkmnopqrstuvwxyz"; //Verification code content 1: letters
$number = "023456789"; //Verification code content 2: numbers
$randcode = ""; //Verification code string initialization
srand((double)microtime()*1000000); //Initialize random number seed
$im = ImageCreate($w, $h); //Create verification image
/*
* Draw Basic framework
*/
$bgcolor = ImageColorAllocate($im, 255, 255, 255); //Set the background color
ImageFill($im, 0, 0, $bgcolor); //Fill the background Color
if($border)
{
$black = ImageColorAllocate($im, 0, 0, 0); //Set border color
ImageRectangle($im, 0, 0, $w -1, $h-1, $black);//Draw the border
}
/*
* Generate random characters bit by bit
*/
for($i=0; $ i<$how; $i++)
{
$alpha_or_number = mt_rand(0, 1); //Letters or numbers
$str = $alpha_or_number ? $alpha : $number;
$which = mt_rand(0, strlen($str)-1); //Which character is taken
$code = substr($str, $which, 1); //Character is taken
$j = !$i ? 4: $j+15; //Draw character position
$color3 = ImageColorAllocate($im, mt_rand(0,100), mt_rand(0,100), mt_rand(0,100)); //Character color then
ImageChar($ im, $fontsize, $j, 3, $code, $color3); //Draw characters
$randcode .= $code; //Add the verification code string bit by bit
}
// Write the verification code string into session
session_start();
$_SESSION['authnum_session'] = $randcode;
/*
* Add interference
*/
for($ i=0; $i<1; $i++)//Draw background interference lines
{
$color1 = ImageColorAllocate($im, mt_rand(0,255), mt_rand(0,255), mt_rand(0,255)); / /Interference line color
ImageArc($im, mt_rand(-5,$w), mt_rand(-5,$h), mt_rand(20,300), mt_rand(20,200), 55, 44, $color1); // Interference line
}
for($i=0; $i<$how*40; $i++)//Draw background interference point
{
$color2 = ImageColorAllocate($im, mt_rand( 0,255), mt_rand(0,255), mt_rand(0,255)); //Interference point color
ImageSetPixel($im, mt_rand(0,$w), mt_rand(0,$h), $color2); //Interference Click
}
//Key code to prevent the problem of 'the image cannot be displayed because of its own errors'
ob_clean();
/*End of drawing*/
Imagegif($im );
ImageDestroy($im);
/*End of drawing*/

Confirmation code calls file sessionValidate.php

Copy code The code is as follows:

session_start();
//On the page, you must first open the session,
//error_reporting (2047);
session_destroy();
//Remove the session so that you can get a new session value every time;
//Using seesion works well and is very convenient
?>





This example is Session verification example

Verification code:

//Print the previous session ;
echo "Previous session:".$_SESSION["authnum_session"]."
";
$validate="";
if( isset($_POST["validate"])){
$validate=$_POST["validate"];
echo "What you just entered is: ".$_POST["validate"]."< br>Status: ";
if($validate!=$_SESSION["authnum_session"]){
//Determine whether the session value is consistent with the verification code entered by the user;
echo "Incorrect input";
}else{
echo "Verified";
}
}
/*
//Print all sessions;
PrintArr($_SESSION);
function PrintArr($aArray){
echo '';<br>print_r($aArray) ;<br>echo '';
}
*/
?>

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