php สอบถามเกี่ยวกับ การใช้คำสั่ง fopen fwrite ถ้าต้องการเขียน text ต่อจากตำแหน่งของ text ล่าสุดโดยที่ข้อมูล text เก่ายังอยู่

$strFileName = "thaicreate.txt";
$objFopen = fopen($strFileName, 'w');
$strText1 = "I Love ThaiCreate.Com Line1\r\n";
fwrite($objFopen, $strText1);
$strText2 = "I Love ThaiCreate.Com Line2\r\n";
fwrite($objFopen, $strText2);
$strText3 = "I Love ThaiCreate.Com Line3\r\n";
fwrite($objFopen, $strText3);

<?php
$filename ="data.xml";

$fn = fopen ( "data.txt", "r" );
while ( ! feof ( $fn ) ) {
	$current = trim ( fgets ( $fn ) );
	$iArray [] = explode ( "*", $current );
}

$count = count ( $iArray );

for($x = 0; $x < $count; $x ++) {
	$newArray [$x] ["title"] = trim ( $iArray [$x] [0] );
	$newArray [$x] ["old_price"] = trim ( $iArray [$x] [1] );
	$newArray [$x] ["price"] = trim ( $iArray [$x] [2] );
	$newArray [$x] ["review"] = trim ( $iArray [$x] [3] );
	$newArray [$x] ["description"] = trim ( $iArray [$x] [4] );
	$newArray [$x] ["image"] = trim ( $iArray [$x] [5] );
	$newArray [$x] ["link"] = trim ( $iArray [$x] [6] );
	$newArray [$x] ["merchant"] = trim ( $iArray [$x] [7] );
}

$xml = "<?xml version=\"1.0\"?>\n";
$xml .= "<item>\n";

foreach ( $newArray as $row ) {
	$xml .= " <product>\n";
	$xml .= " 	<name>" . $row ['title'] . "</name>\n";
	$xml .= " </product>\n";
}

$xml .= "</item>\n";


if (! $handle = fopen ( $filename, 'a' )) {
	echo "Cannot open file ($filename)";
	exit ();
}

if (fwrite ( $handle, $xml . "\n" ) === FALSE) {
	echo "Cannot write to file ($filename)";
	exit ();
}

fclose ( $handle );

?>

<?xml version="1.0" encoding="UTF-8"?>
<item>
<product>
<name>Add this to the file</name>
</product>
</item>