编码验证码phpstrlen
代码如下：
<code> <?phpsession_start ();header("content-type:image/png");$image_width=70;$image_height=18;srand(microtime()*100000);for($i=0;$i<4;$i++){ $new_number=dechex(rand(0,15));}$_SESSION[check_checks]=$new_number;$num_image=imagecreate($image_width,$image_height);imagecolorallocate($num_image,255,255,255);for($i=0;$i<strlen($_SESSION[check_checks]);$i++){ $font=mt_rand(3,5); $x=mt_rand(1,8)+$image_width*$i/4; $y=mt_rand(1,$image_height/4); $color=imagecolorallocate($num_image,mt_rand(0,100),mt_rand(0,150),mt_rand(0,200)); imagestring($num_image,$font,$x,$y,$_SESSION[check_checks][$i],$color);}imagepng($num_image);imagedestroy($num_image);?></code>gd库已开，utf8无bom编码，就是显示不出来
