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Editor to share with you what to do if the CAPTCHA cannot be displayed in PHP. I believe most people don't know much about it, so share this article for your reference. I hope you will gain a lot after reading this article. Let's learn about it together.

The reason why PHP CAPTCHA can not be displayed and its solution

First, if it is utf-8, it is possible that BOM has not been cleared

Second, there is output before Header ("Content-type: image/PNG")

Third, the first line of PHP hides the code, such as spaces, carriage returns and so on. Resolution code:

$image_width=70; / / set the width of the image $image_height=18; / / set the height of the image $new_number=$_GET [num]; / / $new_number=5;$num_image=imagecreate ($image_width,$image_height); / / create a canvas imagecolorallocate ($num_image,255255255); / / set the color of the canvas $black=imagecolorallocate ($num_image,0,0,0); / * / for

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