textarea post gets diffrent result with or without "\"?

textarea post gets diffrent result with or without "\"?

textarea post gets diffrent result with or without "\"?
the same code runs in different pc , get the diffrent result

my systerm is xp , and I post textarea and print it , the result has "\"
befror ' , but I run it in other guy's pc ,the result returns no "\".
why this happen ? how to fix ?

<pre>
<?php
print_r($_POST);
?>
</pre>
<form method="post">
<textarea name="content" id="" cols="30" rows="10">This is kate's
book</textarea>
<input type="submit" />
</form>
in my pc ,get:
this is kate\'s book
in others, get:
this is kate's book