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Reasons and solutions for the PHP verification code not being displayed:
1. If it is utf-8, it is possible that the BOM has not been cleared
2. There is output before Header("Content-type: image/PNG");
3. The first line of PHP hides code, such as spaces, carriage returns, etc.
Solution code:
$image_width=70; //设置图像宽度 $image_height=18; //设置图像高度 $new_number=$_GET[num]; //$new_number=5; $num_image=imagecreate($image_width,$image_height); //创建一个画布 imagecolorallocate($num_image,255,255,255); //设置画布的颜色 $black=imagecolorallocate($num_image,0,0,0); /**/for($i=0;$i<strlen($new_number);$i++){ //循环读取SESSION变量中的验证码 $font=mt_rand(3,5); //设置随机的字体 $x=mt_rand(1,8)+$image_width*$i/4; //设置随机字符所在位置的X坐标 $y=mt_rand(1,$image_height/4); //设置随机字符所在位置的Y坐标 $color=imagecolorallocate($num_image,mt_rand(0,100),mt_rand(0,150),mt_rand(0,200)); //设置字符的颜色 imagestring($num_image,$font,$x,$y,$new_number[$i],$color); //水平输出字符 } header("content-type:image/png"); //设置创建图像的格式 imagepng($num_image); //生成PNG格式的图像 imagedestroy($num_image); //释放图像资源
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