why always 500:internal server error???

I have a php script which runs all fine on localhost,but when I uploaded and run the same script on my web server it gave a internal server error 500,premature end of sdript headersnull)
But it was running fine on my localhost,file permission set to 755 and I had uploaded the file using my web host's online file uploading system.
What might have been the possible reason for its failure...

the script is below
<?php
//WRITING THE FORMATED AND ALTERNATE RSS INPUT FEED
//writing data onto myrss1 text file
$number=date("d-m-Y");
$f1=fopen("myrss1$number.txt","w");
$f2=fopen("rss1.txt","r");$f3=fopen("rss2.txt","r");
$n=1;
while ($n<=4)
{
$n2=1;
while ($n2==1)
{
$data=fgetc($f2);
if ($data=="^")
{$n2=3;}
else
fwrite($f1,"$data");
}
$n3=1;
while($n3==1)
{
$data2=fgetc($f3);
if ($data2=="^")
{$n3=3;}
else
fwrite($f1,"$data2");
}
$n=$n+1;
}
fclose($f1);
fclose($f2);
fclose($f3);

//writing data onto myrss2 file
$f1=fopen("myrss2$number.txt","w");
$f2=fopen("rss3.txt","r");$f3=fopen("rss4.txt","r");
$n=1;
while ($n<=4)
{
$n2=1;
while ($n2==1)
{
$data=fgetc($f2);
if ($data=="^")
{$n2=3;}
else
fwrite($f1,"$data");
}
$n3=1;
while($n3==1)
{
$data2=fgetc($f3);
if ($data2=="^")
{$n3=3;}
else
fwrite($f1,"$data2");
}
$n=$n+1;
}
fclose($f1);
fclose($f2);
fclose($f3);

//CREATING TWO NEW HTML PAGES
//writing the page 1
$f1=fopen("title1.txt","r");$f2=fopen("description1.txt","r");
$title1=fread($f1,4096);$description1=fread($f2,4096);
fclose($f1);fclose($f2);
$hyip1=fopen("hyip-news$number.html","w");
$read=fopen("myrss1$number.txt","r");
$read1=fopen("htmlpart1.txt","r");
while (!feof($read1))
{
$data=fgetc($read1);
fwrite($hyip1,"$data");
}fclose($read1);

fwrite($hyip1,"$title1");

$read2=fopen("htmlpart2.txt","r");
while (!feof($read2))
{
$data=fgetc($read2);
fwrite($hyip1,"$data");
}fclose($read2);

fwrite($hyip1,"$description1");
$read3=fopen("htmlpart3.txt","r");
while (!feof($read3))
{
$data=fgetc($read3);
fwrite($hyip1,"$data");
}fclose($read3);

fwrite($hyip1,"Latest HYIP News for $number");

$read4=fopen("htmlpart4.txt","r");
while (!feof($read4))
{
$data=fgetc($read4);
fwrite($hyip1,"$data");
}fclose($read4);

while (!feof($read))
{
$data=fgetc($read);
fwrite($hyip1,"$data");
}fclose($read);

$read5=fopen("htmlpart5.txt","r");
while (!feof($read5))
{
$data=fgetc($read5);
fwrite($hyip1,"$data");
}fclose($read5);

fwrite($hyip1,"hyip-news2$number.com");

$read6=fopen("htmlpart6.txt","r");
while (!feof($read6))
{
$data=fgetc($read6);
fwrite($hyip1,"$data");
}fclose($read6);

fclose($hyip1);


//writing the page 2

$f1=fopen("title2.txt","r");$f2=fopen("description2.txt","r");
$title2=fread($f1,4096);$description2=fread($f2,4096);
fclose($f1);fclose($f2);
$hyip1=fopen("hyip-news2$number.html","w");
$read=fopen("myrss2$number.txt","r");
$read1=fopen("htmlpart1.txt","r");
while (!feof($read1))
{
$data=fgetc($read1);
fwrite($hyip1,"$data");
}fclose($read1);

fwrite($hyip1,"$title2");
$read2=fopen("htmlpart2.txt","r");
while (!feof($read2))
{
$data=fgetc($read2);
fwrite($hyip1,"$data");
}fclose($read2);

fwrite($hyip1,"$description2");

$read3=fopen("htmlpart3.txt","r");
while (!feof($read3))
{
$data=fgetc($read3);
fwrite($hyip1,"$data");
}fclose($read3);

fwrite($hyip1,"Latest HYIP News for $number<br/> [page 2]");
$read4=fopen("htmlpart4.txt","r");
while (!feof($read4))
{
$data=fgetc($read4);
fwrite($hyip1,"$data");
}fclose($read4);

while (!feof($read))
{
$data=fgetc($read);
fwrite($hyip1,"$data");
}fclose($read);
$read5=fopen("htmlpart5.txt","r");
while (!feof($read5))
{
$data=fgetc($read5);
fwrite($hyip1,"$data");
}fclose($read5);

fwrite($hyip1,"hyip-news$number.html");

$read6=fopen("htmlpart6.txt","r");
while (!feof($read6))
{
$data=fgetc($read6);
fwrite($hyip1,"$data");
}fclose($read6);

fclose($hyip1);
?>

 

are you sure all the corresponding text files are also uploaded ?