PHP Verification Code

<?php//10> Set session, must be at the top of the script session_start ();        $image = Imagecreatetruecolor (100, 30);    1> set captcha picture size function//5> set CAPTCHA color imagecolorallocate (int im, int red, int green, int blue); $bgcolor = Imagecolorallocate ($image, 255,255,255); #ffffff the area of the//6> area filled with int imagefill (int im, int x, int y, int col) (x and Y) is shaded, col represents the color to be painted Imagefill ($image, 0,    0, $bgcolor);    10> Set Variable $captcha _code = "";                7> generates random letters and numbers for ($i =0; $i <4; $i + +) {//set font size $fontsize = 8;            Set the font color, random color $fontcolor = imagecolorallocate ($image, Rand (0,120), Rand (0,120), Rand (0,120));        0-120 Dark Color//Set the values that need to be randomly taken, removing the error-prone values such as 0 and o $data = ' abcdefghigkmnpqrstuvwxy3456789 ';        Take out the value, String intercept method strlen Gets the string length $fontcontent = substr ($data, Rand (0,strlen ($DATA)), 1);                10>.= continuously defines the variable $captcha _code. = $fontcontent;        Set coordinates $x = ($i *100/4) +rand (5,10);        $y = rand (5,10); Imagestring ($Image, $fontsize, $x, $y, $fontcontent, $fontcolor);    }//10> save to SESSION $_session[' authcode ' = $captcha _code; 8> add interference element, set Snowflake point for ($i =0; $i <200; $i + +) {//Set point color, 50-200 color is lighter than digital, do not disturb reading $pointcolor = Imagecolorallocat                E ($image, Rand (50,200), Rand (50,200), Rand (50,200));    Imagesetpixel-draws a single pixel Imagesetpixel ($image, Rand (1,99), Rand (1,29), $pointcolor); }//9> Add interference element, set horizontal for ($i =0; $i <4; $i + +) {//set line Color $linecolor = Imagecolorallocate ($image, rand (80,2        Rand (80,220), Rand (80,220));    Set line, 2.1-wire imageline ($image, Rand (1,99), Rand (1,29), Rand (1,99), Rand (1,29), $linecolor);    }//2> set head, image/png header (' content-type:image/png ');    3>imagepng () establishes the PNG graph function imagepng ($image); 4>imagedestroy () End graph function Destroy $image Imagedestroy ($image);

PHP Verification Code