problem in read xml doc

hi i have below code,,,when i put $string1 in yes.txt file every thing works fine but when i put $string2 in yes.txt some error occurred;
its my code:

[code=php]<?php
$data = <<<EOD
<?xml version=”1.0″?>
<root>

EOD;

$string1=”<DOC>
<DATE>07/31/2009</DATE>
<AUTHOR>FlewByU</AUTHOR>
<TEXT>I just moved to Germany two months ago and bought an 07 MDX from another military member. It has everything I could want. We just returned from a week driving through the Alps and this SUV is simply amazing. Granted, I get to drive it much faster than I could in the states, but even at 120 MPH, it was rock solid. We need the AWD for the snow and the kids stay entertained with the AV system. Plenty of passing power and very comfortable on long trips. Acuras are rare in Germany and I get stares all the time by curious Bavarians wondering what kind of vehicle I have. If you are in the market for a luxury SUV for family touring, with cool tech toys to play with, MDX can’t be beat. </TEXT>
<FAVORITE>The separate controls for the rear passengers are awesome. I can control temp and AV from the front or switch to rear. Sound system is amazing. I will sometimes sit in the driveway and just listen. Also has a 120v outlet in console. Great for us since we live with 220v and need 120 on occasion. </FAVORITE>
</DOC>”;
$string2=”<DOC>
<DATE>08/28/2009</DATE>
<AUTHOR>RDX LOVER</AUTHOR>
<TEXT>I’m a sales rep and drive approximately 40,000-45,000 miles a year for work. I’ve owned the RDX for a little more than two years and have 94,000 miles on it. I LOVE THIS CAR! The quality is excellent, the power & handling is excellent. The features of the tech pkg are great and reliable. I get compliments about this car all the time because of its styling and luxury. As long as you don’t stand on the throttle and use up the turbo all the time, you get respectable gas mileage. I usually get 20-21 mpg in mixed driving conditions. When I’m aggressive I get 18-19 mpg. Due to a sporty suspension some may not like to feel every bump. You get a lot for the money. Compare the features to others. </TEXT>
<FAVORITE>Blue Tooth Technology Backup camera with right side mirror that tilts, which makes this car easy to park. The controls are at your fingertips. Great power. It has a lot of room for a little SUV. </FAVORITE>
</DOC>”;

$fileName = ‘yes.txt’;
file_put_contents($fileName, $string);
$data .= file_get_contents(‘yes.txt’);
$data .= “n</root>”;
$xml = simplexml_load_string($data);
foreach($xml->DOC as $doc) {
echo “<h3>”.$doc->AUTHOR.’ (‘.$doc->DATE.”)</h3>n”;
echo “<p>”.$doc->TEXT.”</p>n”;
echo “<p><i>”.$doc->FAVORITE.”</i>n”;
}
?>[/code]

some thing wrong in string2 ,,, how can i find it?how can i fix it?

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