PHP CAPTCHA
A CAPTCHA is a type of challenge-response test used in computing as an attempt to ensure that the response is generated by a human being.
It is an acronym based on the word “capture” and standing for “Completely Automated Public Turing test to tell Computers and Humans Apart.
Create a CAPTCHA using arithmetic Operators and match the value
Eg i
<?php error_reporting(1); $arr=range(99,9); $brr=range(99,9); $randa=array_rand($arr); $randb=array_rand($brr); $a=$arr[$randa]; $b=$brr[$randb]; $r=$a+$b; $cap=$a."+".$b; if(isset($_POST['b1'])) { if($_POST['t2']==$_POST['t3']) { echo '<center>'.'<font color="blue" size="5">'."Welcome user".'</font>'.'</center>'; } else { echo '<center>'.'<font color="red" size="5">'."Please fill the correct answer".'</font>'.'</center>'; } } ?> <html> <center> <form method="post"> <?php error_reporting(1); echo $cap."="; ?> <input type="hidden" name="t3" value="<?php echo $r; ?>"> <input type="text" name="t2" autofocus><br> <input type="submit" name="b1" value="match"> </form> </center> </html>
Output : Welcome user 30 + 42=
In the above example
First create a variable $arr with multiple values i.e created by range function(using array range( ) function ).
second variable $brr also hold multiple values between “9” to “99”.
Now pass $arr inside array_rand( ) function, it returns a random array index which stores in $randa and $randb variable.
Now call the value of array $arr[$randa] and store it in $a and $b variable.
In next line create a variable $cap which holds a string ($a.”+”.$b)
print the $cap variable it shows two arithmetic numbers seperated by “+”.
Now calculate the value, enter the calculated value in text-box, to check the addition of two numbers is correct or not.
if addition of two numbers entered by user is right it shows a message “Welcome user” otherwise show error message “Please fill the correct answer”.
First create a variable $arr with multiple values i.e created by range function(using array range( ) function ).
second variable $brr also hold multiple values between “9” to “99”.
Now pass $arr inside array_rand( ) function, it returns a random array index which stores in $randa and $randb variable.
Now call the value of array $arr[$randa] and store it in $a and $b variable.
In next line create a variable $cap which holds a string ($a.”+”.$b)
print the $cap variable it shows two arithmetic numbers seperated by “+”.
Now calculate the value, enter the calculated value in text-box, to check the addition of two numbers is correct or not.
if addition of two numbers entered by user is right it shows a message “Welcome user” otherwise show error message “Please fill the correct answer”.
PHP Create CAPTCHA Security Images
Eg ii
<form action="" method="post" >
<table border="0" align="center">
<tr>
<td width="215"> Validation code:</td>
<td width="162">
<?php
$arr= array_merge(range(0,9),range("A","Z"));
//print_r($arr);
for($i=1;$i<=5;$i++)
{
$ch = $arr[array_rand($arr)];
@$captcha=$captcha.$ch;
@$fc=$fc.$ch.",";
}
//echo $fc."<br>";
$nar = explode(",",$fc);
for($i=0;$i<5;$i++)
{
echo $nar[$i];
//echo "<img src='$nar[$i].GIF'/>";
}
if(isset($_POST['match']))
{
if($_POST['img']==$_POST['hid'])
{
echo "<br/><font color='blue'>security code matched</font>";
}
else
{
echo "<br/><font color='red'> try again</font>";
}
}
?>
<tr>
<td>Enter the above code here :</td>
<td> <input name="img" type="text">
</td>
</tr>
<tr>
<td colspan="2" align="center">
<input name="match" type="submit" value="Submit Security code"></td>
</tr>
</table>
<input type="hidden" value="<?php echo $captcha; ?>" name="hid"/>
</form>
</pre>
</div><br/>
Output :
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