PHP Script: Validation, File get Contents and Writing to .doc file - PHP

Here is the PHP script to make this application work, complete with comments:

<?php

//First, check if the web form has been submitted by checking the value of $_POST[ref]

if($_POST[ref] == "texttoword") {

//If the form has been submitted, check if the recaptcha entered by the client is correct.

require_once('recaptchalib.php');

$errors=array();

$privatekey = "***PUT YOUR OWN PRIVATE KEY HERE***";

$resp = recaptcha_check_answer ($privatekey,

$_SERVER["REMOTE_ADDR"],

$_POST["recaptcha_challenge_field"],

$_POST["recaptcha_response_field"]);

if (!$resp->is_valid) {

//Display error back to the client if the recaptcha entered is incorrect.

die('<font color="red">ERROR: The recaptcha code was not entered correctly or expired. If you think it expired or correctly entered; click Recaptcha refresh button to get a new challenge and press submit again.</font>');

}

//Check also if the file uploaded by the client is a text file.

//Check also the file size, it should be less than 100kB.

//Accept file input in terms of plain text from the user. Plain text has a file extension of .txt

if (($_FILES["file"]["type"] == "text/plain") && ($_FILES["file"]["size"] < 100000))

{

if ($_FILES["file"]["error"] > 0)

{

echo "Return Code: " . $_FILES["file"]["error"] . "<br />";

}

else

{

if (file_exists("upload/" . $_FILES["file"]["name"]))

{

echo $_FILES["file"]["name"] . " already exists. ";

}

else

{

move_uploaded_file($_FILES["file"]["tmp_name"],

"upload/" . $_FILES["file"]["name"]);

}

}

}

else

{

//Display error back to the client if the file uploaded is invalid.

die('<font color="red">Invalid file uploaded.</font>');

}

//If there are no errors during the validation done above, then get the posted uploaded file and assign to a PHP variable

$filetoread="upload/" . $_FILES["file"]["name"];

//Extract the text content of the text file using file_get_contents PHP function, and then assigned the extracted text to a PHP variable.

$text_content=file_get_contents($filetoread);

//To prevent file duplication conflict in case several users are downloading the converted file at the same time, use a unique random key appended to the doc file.

//Generate random number between 10,000 and 99999

$uniquerandomkey = mt_rand(10000, 99999);

//Append unique random key to the word file name

$wordfilename= 'convertedtoword'.$uniquerandomkey.'.doc';

//Create a temporary word file in the upload directory and then prepare this for writing

$fp = fopen("upload/$wordfilename", 'w+');

//Assign the text content extracted from file_get_contents to $writetexttowordfile PHP variable

$writetexttowordfile = $text_content;

//Finally write the text content to the newly-created Word file

fwrite($fp, $writetexttowordfile);

//After writing the file, close it.

fclose($fp);

// Now that word file has been created, present the download link to the client.

$file = "upload/$wordfilename";

echo '<h3>Download link</h3>';

echo '<br />';

echo '<a rel="nofollow" href="'.$file.'"><font size="2">Right click here then <b>Save as</b> to Download</a></font>';

echo '<br />';

echo '<br />';

}

//Show error in case the form is not posted.

elseif ($_POST[ref] == "texttoword") {

echo '<font color="red">This form is not posted.</font>';

}

?>

</font>

</body>

</html>