Solve the Problem of unrealistic php session verification code.

Solve the Problem of unrealistic php session verification code.

At the beginning, the image is not displayed, but a split image is displayed. It may be caused by the following reasons:

1) Add the following code before header ("Content-type: image/png ");

ini_set('display_errors', 'Off');

I am caused by the above problems.

The code of the image that generates the verification code is attached.

<? Php ini_set ('display _ errors ', 'off'); header ("Content-type: image/png"); session_start (); $ _ SESSION ['code'] = 'null'; // initialize $ width = '58 '; $ height = '22'; // $ code = ''; $ tmptext = ''; $ bordercolor =''; for ($ I = 0; $ I <4; $ I ++) {$ tmptext = rand (0, 9 ); $ code. = $ tmptext;} $ _ SESSION ['code'] = $ code; // The following three poems prevent the browser from caching @ header ("Expires:-1 "); @ header ("Cache-Control: no-store, private, posc-check = 0, pre-check = 0, max-age = 0", FALSE); @ heade R ("Pragma: no-cache"); if (function_exists ('imagecreate') & function_exists ('imagecolorset') & function_exists ('imagecopyresized ') & function_exists ('imagecolorallocate') & function_exists ('imagesetpixel ') & function_exists ('imagechar') & function_exists ('imagecreatefromgif ') & function_exists ('imagepng ') {$ im = imagecreate ($ width, $ height); $ backgroundcolor = imagecolorallocate ($ im, 255,255, 25 5); $ numorder = array (,);/** shuffle will disrupt the array */shuffle ($ numorder);/** array_flip will return an array to be reversed, key value processed */$ numorder = array_flip ($ numorder); $ x = ''; $ y =''; $ text_color = ''; for ($ I = 1; $ I <= 4; $ I ++) {$ x = $ numorder [$ I] * 13 + mt_rand (0, 4)-2; $ y = mt_rand (50,255); $ text_color = imagecolorallocate ($ im, mt_rand (50,255), mt_rand (50,255), mt_rand )); /** draw characters in the $ im diagram. 5 indicates the font size $ x + 5 */imagechar ($ im, 5, $ x + 5, $ y + 3, $ code [$ nu Morder [$ I], $ text_color);} $ linenums = mt_rand (10, 32); for ($ I = 0; $ I <= $ linenums; $ I ++) {$ linecolor = imagecolorallocate ($ im, 255, mt_rand (0,255), mt_rand (0,255); $ linex = mt_rand (0,255); $ liney = mt_rand (0,255 ); imageline ($ im, $ linex, $ liney, $ linex + mt_rand ()-2, $ liney + mt_rand ()-2, $ linecolor );} for ($ I = 0; $ I <40; $ I ++) {$ pointcolor = imagecolorallocate ($ im, mt_rand (0,255), mt_rand (0,255), mt_rand (0,255) ); Imagesetpixel ($ im, mt_rand (0, $ width), mt_rand (0, $ height), $ pointcolor);} $ bordercolor = imagecolorallocate ($ im, 150,150,150 ); imagerectangle ($ im, 0, 0, $ width-1, $ height-1, $ bordercolor); imagepng ($ im); imagedestroy ($ im) ;}?>

2) the variable is not initialized.

3) add header ("Content-type: image/png ");

Ob_clean ();

Method 2 and 3 do not guarantee that the problem can be solved, which is for reference only.