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PHP Realizes Login Verification Code Verification Function

  • 2021-10-13 06:45:11
  • OfStack

The verification code is realized by using SESSION function in PHP.

Declare a function at the top session_start(); Tell the server that we want to use the function. 


session_start();

Next, we use the code realized by verification code. Here, use the code of English numbers as an example. 


$image = imagecreatetruecolor(100, 30); // Create 1 A 100 × 30 Canvas of 
$white = imagecolorallocate($image,255,255,255);// White 
imagefill($image,0,0,$white);// Covered with black canvas

Then, before the implementation of the verification code, a null variable is declared to store the verification code. 


$session = ""; // Null variable   , store the verification code 
for($i=0;$i<4;$i++){
 $size = 6;
 $x = $i*25+mt_rand(5,10);
 $y = mt_rand(5,10);
 $sizi_color = imagecolorallocate($image,mt_rand(80,220),mt_rand(80,220),mt_rand(80,220));
 $char = join("",array_merge(range('a','z'),range('A','Z'),range(0,9)));
 $char = str_shuffle($char);
 $char = substr($char,0,1);
 imagestring($image,$size,$x,$y,$char,$sizi_color);
 $session .= $char ; // Put every verification code 1 Assign a value to a variable 
}
 $_SESSION['session'] = $session; // The value of this variable is equal to the value entered by the user 

for($k=0;$k<200;$k++){
 $rand_color = imagecolorallocate($image,mt_rand(50,200),mt_rand(50,200),mt_rand(50,200));
 imagesetpixel($image,mt_rand(1,99),mt_rand(1,29),$rand_color);
}
for($n=0;$n<5;$n++){
 $line_color = imagecolorallocate($image,mt_rand(80,220),mt_rand(80,220),mt_rand(80,220));
 imageline($image,mt_rand(1,99),mt_rand(1,29),mt_rand(1,99),mt_rand(1,29),$line_color);
}
header('content-type:image/png');// Set the file output format 
imagepng( $image ); // With png Format output $image Image 
imagedestroy( $image ); // Destroy images

Use POST to receive the verification code. The strtolower function makes the server case insensitive. This can effectively reduce the input error rate of users. 


if(isset($_POST['session'])){
 session_start();
 if(strtolower($_POST['session'])==strtolower($_SESSION['session'])){
  echo'<font color="#0000CC"> Enter correctly </form>';
 }else{
  echo '<font color="#CC0000"><b> Input error </b></font>';
 }
 exit();
}

Here is the page code for HTML. 


<!DOCTYPE html>
<html>
<head>
 <meta charset="utf-8"/>
 <title> Confirm verification code </title>
</head>
<body>
 <form method="post" action="./tushu.php">
 <p> Verification code picture :<img id="img" border="1" src="http://localhost//xxx.php" width="100" height="30"></p>
 <a href="javascript:void(0)" rel="external nofollow"  onclick="document.getElementById('img').src='http://localhost//xxx.php'"> Can't see clearly? Change 1 A </a>
 <p> Please enter the verification code in the picture: <input type="text" name="session" value=""/></p>
 <p><input type="submit" value=" Submit " style="padding:6px 10px;"></p>
 </form>
</body>
</html>

Summarize

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