PHP verification code generation and verification example

Verification code is a common feature in Web, such as registration, login, or message page. You need a registration code to verify the legality of the current operator. We will see that some websites do not have verification codes, but that is more advanced verification. Let's look at the common verification code generation and use methods.

1. A simple verification code instance

1.1 display the verification code picture

The Code is as follows:	Copy code
<? Php $ Num = intval (mt_rand (1000,9999 )); For ($ I = 0; $ I <4; $ I ++) {Echo " ";} ?>

1.2 verification process

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If (strval ($ inputyzm )! = Strval ($ num )) { Echo "<script> alert ('verification code is incorrect! '); History. go (-1); </script> "; Exit; }

2. Example of a Chinese character Verification Code

2.1 display the verification code picture

The Code is as follows:	Copy code
<? Php $ Str = "Han", "Word", "Verification", "certificate", "Code"); // you can define the content and number of Chinese characters. $ Word = strlen ($ str )); For ($ I = 0; $ I <4; $ I ++) { $ Num = rand (0, $ word ); $ Img = $ img. " "; $ Pic = $ pic. $ str [$ num]; } >

2.2 assign the generated random string to a hidden field

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<Input type = "hidden" name = "yzm" value = "<? Php echo $ pic ;? /> ">

2.3 define a check () function

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<Script language = "javascript"> Function check (form) { If (form. yzm. value = ""){ Alert ("Enter the Verification Code "); Form. yzm. focus (); Return false; } If (form. yzm. vale! = Form. yz. value) {Alert ("Incorrect verification code "); Form. yzm. focus (); Return false; } } </Script>

View a complete instance

Php verification code generation and call examples are frequently used during development. Record them.

1. File code. php generated by the Verification code

The Code is as follows:

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<? Header ("Content-type: image/png "); // Define the header and declare the image file, preferably png, without copyright concerns; // Generate a new four-digit integer Verification Code Session_start (); // enable session; Authnum_session = ''; Str = 'abcdefghijkmnpqrstuvwxyz1234567890 '; // Define the numbers and letters used to display on the image; L = strlen (str); // obtain the string length; // Cyclically and randomly extract four letters and numbers defined above; For (I = 1; I <= 4; I ++) { Num = rand (0 L-1 ); // A number is randomly selected at a time. From the first word to the maximum length of the string, // Minus 1 is because the truncation character starts from 0, so that any 34 characters may be listed in it; Authnum_session. = str [num]; // Connects the characters obtained from numbers to a total of four digits; } Session_register ("authnum_session "); // It is good to use the session for verification. register the session and name it authnum_session, // If other pages contain the image // It can be called through _ SESSION ["authnum_session "] // Generate the verification code image, Srand (double) microtime () * 1000000 ); Im = imagecreate (50, 20); // image width and height; // Black, white, and gray colors are used; Black = ImageColorAllocate (im, 0, 0 ); White = ImageColorAllocate (im, 255,255,255 ); Gray = ImageColorAllocate (im, 200,200,200 ); // Print the four-digit integer verification code into the image Imagefill (im, 68, 30, gray ); // Comment out the line without interfering with the line; Li = ImageColorAllocate (im, 220,220,220 ); For (I = 0; I <3; I ++) {// Add three interference lines; or do not; depending on the situation, because it may affect user input; Imageline (im, rand (), rand (), rand (20, 40), rand (), li ); } // The Position of the character in the image; Imagestring (im, 5, 8, 2, authnum_session, white ); For (I = 0; I <90; I ++) {// Add interference pixels Imagesetpixel (im, rand () % 70, rand () % 30, gray ); } ImagePNG (im ); ImageDestroy (im ); ?>

For the above Code, refer to the following article:
Php image Verification Code
Php verification code generation example
Use php to generate a verification code with a snowflake background

2. sessionValidate. php

The Code is as follows:

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<? Php Session_start (); // Enable the session first at the top, // Error_reporting (2047 ); Session_destroy (); // Remove the session to get the new session value every time; // Use seesion for good results and convenience ?> <Html> <Head> <Title> session image verification instance </title> </Head> <Body> This example is a session verification instance. <Form action = "" method = "post"> Verification Code: <input type = "text" name = "validate" value = "" size = 10> <br> <Input type = "submit"> </Form> <? Php // Print the previous session; Echo "previous session: <B>". _ SESSION ["authnum_session"]. "</B> <br> "; Validate = ""; If (isset (_ POST ["validate"]) { Validate = _ POST ["validate"]; Echo "you just entered:". _ 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 "<font color = red> incorrect input </font> "; } Else { Echo "<font color = green> Verification passed </font> "; } } /* // Print all sessions; PrintArr (_ SESSION ); Function PrintArr (aArray ){ Echo '<xmp> '; Print_r (aArray ); Echo '</xmp> '; } */ ?>