PHP - Plagiarism Checler

Any body here who can help me to make a plagiarism checker in php? that can accurately get the site of the content that is copied from internet. thanks in advance. godbless.

Hello guys, i have a problem that i am trying to solve myself for the entire past week. I am not a php programmer and i wish you can help me.
There is a russian project called Crot Anti-Plagiarism, it is a open source moodle plugin. I started to use it and it is a really nice feature. The problem is that there are quite few people that are developing it and new features are coming once a year...
I see a big "hole" in this project (at least for me) : The plugin checks for plagiarism in the file that you submit only once, if a student resubmits the file it doesn't see that and you need to start the plugin's test again for all the files which is time consuming if you have a lot of submitted files to check.
I would like to add a function that will check if a file changed his modified date , if yes - mark for checking, if no - skip the checking.
I already added a similar function that checks if the name has changed, but it seems harder to check it by uploaded time(modified time).
Things i have already done:
I added a new column "assignment_submissions_timemodified" in database.
I added a new function that records the "time modified" of the file in the database.
But i can't add and i cannot make the comparison between the date of the first time the file submitted versus the date of the second time the same file was resubmitted.
Alright no more bullsh**t here is the code: (there are 3 comments that shows what i've changed, starting with  //my job...)
Thanks a lot!
Code: [Select]
$apath= $CFG->dataroot."/$assignment->course/moddata/assignment/$asubmission->assignment/$asubmission->userid";
        $timemodified= filemtime($apath);    //my job... it checks the file's modified time.
$files = scandir($apath, 1);
if (! $unprocessedsubm = get_record("crot_submissions", "submissionid", $asubmission->id, "crot_submission_file_name", $files[0], "assignment_submissions_timemodified", $timemodified))  //my job...now i guess here is the problem ( "assignment_submissions_timemodified", $timemodified)
{
        echo "$timemodified";
        echo "$unprocessedsubm";
print_r($unprocessedsubm);
echo "\nsubmission $asubmission->id was not processed yet. start processing now ... \n" ;
$atime = microtime();
$atime = explode(" ",$atime);
$atime = $atime[1] + $atime[0];
$astarttime = $atime;
if(!count($files))break;
//TODO we should verify if filename changed
//TODO add loop on the documents folder as well as loop for unzipping
$apath = $apath."/$files[0]";
// call tokenizer to get plain text and store it in crot_submissions
$atext = tokenizer ($apath);
// update the crot_submissions table
// delete if exists
delete_records("crot_submissions", "submissionid", $asubmission->id);
// insert the new record
$record->submissionid=$asubmission->id;
$record->updated = time();
$record->crot_submission_file_name = $files[0];                                   
$record->assignment_submissions_timemodified = $timemodified;        //this is my job.... it is recording the date as it has to.
$submid = insert_record("crot_submissions", $record);
// insert into documents
$docrecord->crot_submission_id = $submid;
Also i have attached the whole file crot_crone.php.