PHP to use the GD library to draw pictures, make verification code browser can not output

1, the code is as follows:

<?php

function fillrandomstring () {

Generate Verification Code

$char = Array_merge (range (0, 9), Range ("A", "Z"), Range ("A", "Z"));

Talk about string $char upset

$luan = Str_shuffle (Implode ("", $char));

Randomly take four bits from a string

Return substr ($luan, 0,4);

}

Create a canvas

Header (' content-type:image/png ');

$height = 20;

$width = 80;

$image = Imagecreate ($width, $height);

$black = imagecolorallocate ($image, 0, 0, 0);

$white = Imagecolorallocate ($image, 255, 255, 255);

Draw a picture rectangle

Imagefilledrectangle ($image, 1, 1, $width-2, $height-2, $white);

padding string

Imagestring, $image, 4, fillrandomstring (), $black);

Output picture

Imagepng ($image);

Destroying pictures

Imagedestroy ($image);

However, the output on the browser is not displayed because the cache was not cleaned before output to the browser

Add code Ob_clean () before the header ();

This article is from the "Chensir" blog, make sure to keep this source http://sourliki.blog.51cto.com/4838492/1557635

PHP to use the GD library to draw pictures, make verification code browser can not output