Detailed explanation of how to use the GD library in PHP to complete the verification code effect tutorial

This article mainly introduces the relevant information on how to use the GD library to create verification codes in PHP (clicking on the verification code or not seeing it clearly will refresh the verification code), friends in need can refer to it

This is the use The page where the GD library generates the verification code

test.PHP

<?php 
header(&#39;Content-Type:image/jpeg&#39;); 
 $img = imagecreatetruecolor(100, 40); 
 $black = imagecolorallocate($img, 0x00, 0x00, 0x00); 
 $green = imagecolorallocate($img, 0x00, 0xFF, 0x00); 
 $white = imagecolorallocate($img, 0xFF, 0xFF, 0xFF); 
 imagefill($img,0,0,$white); //生成随机的验证码 
 $code = &#39;&#39;; 
 for($i = 0; $i < 4; $i++) { $code .= rand(0, 9); } 
 imagestring($img, 5, 10, 10, $code, $black); 
 //加入噪点干扰 
 for($i=0;$i<50;$i++) { 
  imagesetpixel($img, rand(0, 100) , rand(0, 100) , $black); 
  imagesetpixel($img, rand(0, 100) , rand(0, 100) , $green); 
 } //输出验证码 header("content-type: image/png"); 
 imagepng($img); 
 imagedestroy($img); 
?>

This is the verification code that can be partially refreshed after clicking the verification code or seeing it clearly

test2.php

<script type="text/javascript"> 
 function shuaxin() 
 { 
  document.getElementById(&#39;code&#39;).src = "test.php?"+Math.random(); 
 } 
</script> 
<input type="text"><br /> 
<img  id="code" src="test.php" onclick="shuaxin()" / alt="Detailed explanation of how to use the GD library in PHP to complete the verification code effect tutorial" > 
<span onclick="shuaxin()">看不清？</span><br />

As shown below:

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