PHP verification code @ symbol

PHP verification code @ symbol PHPcode & lt ;? Phpsession_start (); for ($ i0; $ I & lt; 4; $ I ++) {@ $ rand. dechex (rand (160); [email & #; protected], the image cannot be displayed .} @ $ _ SESSION [check_p help PHP verification code @ symbol

PHP code

PHP code

[Email protected]? Incorrect prompt
Notice: Use of undefined constant code-assumed 'code' in F: \ wamp \ apps \ project \ code_sub.php on line 3

Notice: Use of undefined constant code-assumed 'code' in F: \ wamp \ apps \ project \ code_sub.php on line 4

Notice: Use of undefined constant check_pic-assumed 'check _ pic 'in F: \ wamp \ apps \ project \ code_sub.php on line 4

[Email protected] What is the error?


------ Solution --------------------
Quote $ _ SESSION ["check_pic"]

Undefined constant refers to an undefined constant, which is treated as a constant without quotation marks.
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PHP code

For ($ I = 0; $ I <4; $ I ++) {$ rand = ''; $ rand. = dechex (rand (); [email protected], the image cannot be displayed. } $ _ SESSION ['Check _ pic '] = $ rand; [email protected] and all are garbled characters.
------ Solution --------------------
$ Rand. =

This variable is used when no value is assigned, so the notice error occurs. The image is binary and the notice is text. The combination of the two causes the image to fail to be displayed.

Solution:
Assign a value to $ rand first.

$ Rand = '';


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PHP code
   
   
Session_start (); $ rand = ''; for ($ I = 0; $ I <4; $ I ++) {$ rand. = dechex (rand (); [email protected], the image cannot be displayed. } $ _ SESSION ['Check _ pic '] = $ rand; [email protected] and all are garbled characters. $ Im = imagecreatetruecolor (255,255,255, 30); $ bg = imagecolorallocate ($ im, 0); $ te = imagecolorallocate ($ im,); imagestring ($ im, 0, $ rand, $ te); header ("content-type: image/jpeg"); imagejpeg ($ im );
------ Solution --------------------

    
     Discussion
     
PHP code
     

     

     Session_start ();
     
    
     
For ($ I = 0; $ I <4; $ I ++ ){
     
@ $ Rand. = dechex (rand (); [email protected], the image cannot be displayed.
     
}
     
@ $ _ SESSION [check_pic] = $ rand; [email protected] and all are garbled characters. ......