Description:
------------
The example A runs correctly .It's output on browse is like this
: int(0) test
and the output in file "test.txt" is
:
1406285601


The example B doesn't runs correctly .It's output on browse is 
: int(0) test 
    which with no problem
but the output in file "test.txt" is like that
:
1406285917
1406285919
    it means that all the codes executed twice except the line contains "echo".I try replaced "file_put_contents " to other operation likes mysql's insert ,it  still executed twice and the database inserted two records;

Test script:
---------------
<?php    //example A
sleep(2);
echo 'test';
file_put_contents("test.txt",time()."\r\n", FILE_APPEND);
?>



<?php   // example B which some codes execute twice
var_dump(0);
sleep(2);
echo 'test';
file_put_contents("test.txt",time()."\r\n", FILE_APPEND);
?>