why can't detect the tab delimiter?

[00009261]

$filename="../../../cgi-bin/members03493199/".$Nickname.".cgi";
$fd = fopen ($filename, "r");
while (!feof ($fd))
{
$buffer = fgets($fd, 4096);

// the original text is :test test1, betwwen the words are separateb by a tab, \t

echo $buffer[0];     //this one has output "t"

if($buffer[3] ==  '\t')
   echo "yeah";
if($buffer[4] ==  '\t')
   echo "yeah";
 if($buffer[5] ==  '\t')
   echo  "yeah";
 if($buffer[6] ==  '\t')
   echo "yeah";

}
fclose ($fd);

however, there is no output "yeah"when I run the code, the server seems cannot detect the tab.

please help me.
thank you.

[hand]

<?
$filename="../../../cgi-bin/members03493199/".$Nickname.".cgi"; 
$fd = fopen ($filename, "r"); 
while (!feof ($fd)) { 
	$buffer = fgets($fd, 4096); 
	echo "$buffer<br>"; 	//prints the whole line
	if (eregi ("\t",$buffer)) {
		print "could find tab<br>";
		$seperate = explode("\t",$buffer);

	while (list($key,$val)=each($seperate)) {
		echo "#$key -> $val :: ";
	}
} else {
	print "sorry couldnt find any tab<br>";
}
print "<hr>";
} 
fclose ($fd); 
?>