Visitor Counts in PHP stopped working suddenly

Question

I have visitor count script on my website.

It was working well until noon (ITC), but now it is not working, also all the files of counts are now not having any text, even a single character.

My Codes:

<?php
if (file_exists('date.txt')) {     
date_default_timezone_set('Asia/Calcutta');
$cdatel = date('Y-m-d', time());

$dthandle = fopen("date.txt", "r"); //reads date
$date =  fread($dthandle,filesize("date.txt"));
fclose ($dthandle);
$tthandle = fopen("total.txt", "r"); //reads total count
$ttcounter =  fread($tthandle,filesize("total.txt"));
fclose ($tthandle);
$ttcounter++; //+1 for new count in total
$ttl = $ttcounter;
$tthandle = fopen("total.txt", "w" ); //write for total count
fwrite($tthandle,$ttcounter);
fclose ($tthandle);
if($cdatel == $date){ //checks whether date in file is same as current date
$handle = fopen("today.txt", "r"); //reads todays count
$counter =  fread($handle,filesize("today.txt"));
fclose ($handle);
$yhandle = fopen("yesterday.txt", "r"); //reads todays count
$yv =  fread($yhandle,filesize("yesterday.txt"));
fclose ($yhandle);
$counter++; //+1 for new count in todays
$tdy = $counter;
$handle = fopen("today.txt", "w" ); //write for todays count
fwrite($handle,$counter);
fclose ($handle); 
}
else{
$ttyhandle = fopen("date.txt", "w" );
fwrite($ttyhandle,$cdatel);
fclose ($ttyhandle);
$ttyhandle = fopen("today.txt", "r");
$tdycounter =  fread($ttyhandle,filesize("today.txt"));
fclose ($ttyhandle);
$zero = "0";
$tzhandle = fopen("today.txt", "w" );
fwrite($tzhandle,$zero);
fclose ($tzhandle); 
$ttyhandle = fopen("yesterday.txt", "w" );
fwrite($ttyhandle,$tdycounter);
fclose ($ttyhandle);
?>
<meta http-equiv="refresh" content="0; ./sitemap-generator.php">
<?php
}
} 
?>