I'd really appreciate it if someone could help me with this, thanks :-)
Hello Carly,
I am assuming that you are looking to do this on your web based forms to prevent form based attacks.
You could use the "Capatcha" based code to do this. It is a very common practice to use images and other sorts of human readable identifiers before allowing a submit:
Create Image:
<?php
session_start();
define('CAPYAINC','homedir/'); // the directory where the fonts and bg image are stored
define('CAPYAURI','http://domian.com'); // the web uri where the captcha image will be located
define('CAPYADIR','/homedir/domain.com/htdocs/images/'); the directory where the captcha image will be stored
function askapache_captcha($type=1,$numletters=4,$fontsize=22){
$capya_string=capya_string($numletters); // the letters and numbers displayed on captcha
$capya_bgfile=CAPYAINC.'n.png'; // the background image for the captcha
$capya_filename='askapache-'.rand(1111,999999).'.jpg'; // the filename of finished captcha
$capya_file=CAPYADIR.$capya_filename; // the full path to finished captcha
$capya_uri=CAPYAURI.$capya_filename; // the public web address to finished captcha
$rgb[0]=array(204,0,0);
$rgb[1]=array(34,136,0);
$rgb[2]=array(51,102,204);
$rgb[3]=array(141,214,210);
$rgb[4]=array(214,141,205);
$rgb[5]=array(100,138,204);
// create image from background image
$image=imagecreatefrompng($capya_bgfile);
// store the md5 of the captcha string
$_SESSION['askapache_captcha'] = md5($capya_string);
// add chars to captcha image
$g=$fontsize;
for($i=0; $i<$numletters; $i++){
$L[]=substr($capya_string,$i,1); // each char from string into individual variable
$A[]=rand(-20, 20); // random angle for each char
$F[]=CAPYAINC.rand(1, 10).".ttf"; // random font for each char
$C[]=rand(0, 5); // random color for each char
$T[]=imagecolorallocate($image,$rgb[$C[$i]][0],$rgb[$C[$i]][1],$rgb[$C[$i]][2]); // allocate colors for chars
imagettftext($image, $fontsize, $A[$i], $g, $fontsize+15, $T[$i], $F[$i], $L[$i]); // write chars to image
$g+=$fontsize+10;
}
// save jpeg image to public web folder
imagejpeg($image, $capya_file);
if($type===1){
// output the image url
echo '<p><img src="'.$capya_uri.'" alt="" width="150" height="50" /><label for="capya" class="S"><input id="capya" name="capya" type="text" value="" size="5" class="S" style="width:150px" maxlength="5" /></label></p>';
} else echo '<img src="'.$capya_uri.'" alt="" width="150" height="50" />';
// destroy image
imagedestroy($image);
// delete all captcha images at 12 and 3 oclock if more than 100 are found
$dt=date('g');
if(($dt==12)||($dt=='12'))capya_cleanup();
else if(($dt==3)||($dt=='3'))capya_cleanup();
}
function capya_cleanup(){
$files=glob(CAPYADIR."apache*.jpg");
if(sizeof($files)>100){
foreach ($files as $filename) {
unlink($filename);
//echo "$filename size " . filesize($filename) . "\n";
}
}
}
function capya_string($len){
$str='';
for($i=1; $i<=$len; $i++) {
$ord=rand(48, 90);
if((($ord >= 48) && ($ord <= 57)) || (($ord >= 65) && ($ord<= 90))) $str.=chr($ord);
else $str.=capya_string(1);
}
return $str;
}
?>
Now Verify:
<?php
if(md5($_REQUEST['capya'])===$_SESSION['askapache_captcha']){
echo 'verified, continue processing script';
}else{
echo 'incorrect, stop processing script';
}
?>