PHP Production Verification Code

Purpose of Study:
Block machine requests to ensure that the business is not disturbed by machine submission requests.
Why to block:
In General Service-side business, write requests consume much more than read requests .
Technical points:
1. Implementation of the basemap and adding interference elements
2. Generate Validation Content
3. Verify that the content is stored on the server
4. Verifying the efficacy of the content

To implement a basemap:

Code:

<?php   $img  = Imagecreatetruecolor (100 , 30 ); //size   $bgColor  = imagecolorallocate ( $img , 0x00 , 0x00 , 0x00 ); Span class= "hljs-comment" >//background color  imagefill ( $img , 0 , 0 ,  $bgColor ); //Fill Color  header ( ' content-type:image/png ' ); Imagepng ( $img ); //destroy  Imagedestroy ( $img );   

Increase point interference and line interference:

<?php$img= Imagecreatetruecolor ( -, -);//Size$bgColor= Imagecolorallocate ($img,0xFF,0xFF,0xFF);//Background colorImagefill ($img,0,0,$bgColor);//Fill Color//Add random numbers for($i=0;$i<4;$i++){$numberSize=6;$numberColor= Imagecolorallocate ($img,Rand(0, -),Rand(0, -),Rand(0, -));//Dark zone    //Position not coincident    $x= ($i*100/4)+Rand(0,5);$y=Rand(5,Ten); Imagestring ($img,$numberSize,$x,$y,Rand(0,9),$numberColor);}//Increase point interference for($i=0;$i< $;$i++){//Interference color    $pointColor= Imagecolorallocate ($img,Rand( -, $),Rand( -, $),Rand( -, $)); Imagesetpixel ($img,Rand(0, -),Rand(0, -),$pointColor);}//Increase line interference for($i=0;$i<4;$i++){//Interference color    $lineColor= Imagecolorallocate ($img,Rand( the, $),Rand( the, $),Rand( the, $)); Imageline ($img,Rand(0, -),Rand(0, -),Rand(0, -),Rand(0, -),$lineColor);} Header' Content-type:image/png '); Imagepng ($img);//DestroyImagedestroy ($img);

Precautions:
Interference information must control the color, do not "distracting."

Verifying information through session storage

Goal:
Record verification code information on the server to facilitate user input
Method:
Session_Start ()
Precautions:
1.session_start** must be at the top of the script * *
2. Multi-server situation, need to consider centralized management session information

Solve the garbled problem yourself: Convert to UTF-8 no BOM format encoding.

The image and video verification principle is the same, just maintain a picture material library and its corresponding session relationship only.

implementation of Chinese verification Code :
Realize:
Imagettftext () method that relies on the GD library
Attention:
1.GBK encoding, you need to convert Chinese through iconv () to UTF-8
2. The selected TTF file needs to support Chinese

In Utf-8, does the Chinese font account for 3 bytes? (not sure).

PHP Production Verification Code