A tutorial on PHP Captcha Experience

<?php/** Captcha Experience *date:2011-02-19*author:fdipzone*/class captcha{//class startprivate $sname = ';p ublic function __construct ($sname = ") {//$sname captcha Session Name$this->sname = $sname = ="? ' M_captcha ': $sname;} /** Generate CAPTCHA image * @param int$length * @param array$param parameters * @return img*/public function Create ($length =4, $param =array ()) {Header ("Content-type:image/png"), $authnum = $this->random ($length);//Generate Authenticode characters. $width = Isset ($param [' width '] )? $param [' width ']: 13;//text width $height = isset ($param [' height '])? $param [' Height ']: 18;//text height $pnum= isset ($param [' pnum '])? $param [' Pnum ']: 100;//number of interfering pixels $lnum= isset ($param [' lnum '])? $param [' Lnum ']: 2;//number of interfering lines $this->captcha_session ($this->sname, $authnum);//will be written in SESSION$PW = $width * $length + $PH = $height +6; $im = Imagecreate ($PW, $ph);//imagecreate () creates a new image with a blank image size of x_size and y_size.  $black = Imagecolorallocate ($im, 238,238,238);//Set background color $values = Array (mt_rand (0, $PW), Mt_rand (0, $ph), Mt_rand (0, $PW), Mt_rand (0, $ph), Mt_rand (0, $PW), Mt_rand (0, $ph), Mt_rand (0, $PW), Mt_rand (0, $ph), Mt_rand (0, $PW), Mt_rand (0, $ph), Mt_rand (0, $PW), Mt_rand (0, $ph)); Imagefilledpolygon ($im, $values, 6, Imagecolorallocate ($im, Mt_rand (170,255), Mt_rand (200,255), Mt_rand (210,255))); /Set up a disturbed polygon basemap/* Text */for ($i = 0; $i < strlen ($authnum); $i + +) {$font = Imagecolorallocate ($im, Mt_rand (0,50), Mt_rand (0,150 ), Mt_rand (0,200));//Set text color $x = $i/$length * $PW + rand (1, 6);//set random x Coordinate $y = rand (1, $PH/3);//set random y-coordinate imagestring ($im, Mt_r and (4,6), $x, $y, substr ($authnum, $i, 1), $font); }/* Add interfering pixel */for ($i =0; $i < $pnum; $i + +) {$dist = Imagecolorallocate ($im, Mt_rand (0,255), Mt_rand (0,255), Mt_rand (0,255 )); Set the dot color Imagesetpixel ($im, Mt_rand (0, $PW), Mt_rand (0, $ph), $dist); }/* Join the */for ($i =0; $i < $lnum; $i + +) {$dist = Imagecolorallocate ($im, Mt_rand (50,255), Mt_rand (150,255), Mt_rand ( 200,255)); Setup Line Color Imageline ($im, Mt_rand (0, $PW), Mt_rand (0, $ph), Mt_rand (0, $PW), Mt_rand (0, $ph), $dist);} Imagepng ($im);//Export the image to a browser or file Imagedestroy ($im) in PNG format;//Destroy an image}/** check the certificate *@param String $captcha Experience * @param int $flag after successful 0: do not clear session 1: Clear session* @return boolean*/public function Check ($captch A, $flag =1) {if (empty ($captcha)) {return false;} Else{if (Strtoupper ($captcha) = = $this->captcha_session ($this->sname)) {//Test if ($flag ==1) {$this Captcha_session ($this->sname, ');} return true;} Else{return false;}}} /* Generates a random number function * @paramint $length the number of strings that need to be randomly generated * @returnString */private function random ($length) {$hash = '; $chars = ' ABCDEFGHIJKLMNPQRSTUVWXYZ23456789 '; $max = strlen ($chars)-1;for ($i = 0; $i < $length; $i + +) {$hash. = $chars [Mt_rand (0 , $max)];} return $hash;} /** Experience the Session method * @paramString $namecaptcha session name* @paramString $value * @returnString */private function captcha _session ($name, $value =null) {if (Isset ($value)) {if ($value!== ") {$_session[$name] = $value;} Else{unset ($_session[$name]);}} Else{return isset ($_session[$name])? $_session[$name]: ';}} Class end?>

Demo

<?session_start (); require_once (' Captcha.class.php '); $obj = new Captcha ($sname); # Create Captcha like Sname to save the session name of CAPTCHA, leave it blank, and leave it as ' M_captcha ' $obj->create ($length, $param); # Create a captcha and output a picture # $ Length is CAPTCHA, can be left blank, implicitly 4/* $param = Array (' width ' = 13captcha character width ' height ' + 18captcha character height ' pnum ' = 100 Disturb dot ' Lnum ' + 2 Dry line number can be left blank */$obj->check ($captcha, $flag); # Check to see if the user input is correct, true or false# $captcha for the user to enter the certificate, required # $flag Can be left blank, 1 #1: When proven successful, self-purge captcha session#0: When proven successful, do not clear the CAPTCHA session and use Ajax to check?>

This article explains the content of PHP Captcha experience, and more about it, please follow the PHP Chinese web.

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