Description:
------------
Hello,

Create a class and implement Serializable, then use the serialize function to return the value of serialize($this), apache crashes with an internal server error, the apache error log reports a Premature end of script headers error.

If line 17 is commented then the apache server does not crash.

Test script:
---------------
<?php
/**Simple class that is serializable and implements the serializable interface */
class ImplementsSerializable implements Serializable {
    /** returns the serialization of itself */
    public function serialize() {
        return serialize($this);
    }
    /** returns unserialized object passed in $serialized */
    public function unserialize($serialized) {
        return unserialize($serialized);
    }
}
/** Create a new ImplementSerializable object */
$serializable = new ImplementsSerializable();
/** Store the serialized value in $serialized, this causes apache to crash, with a
 *  Premature end of script headers error in the apache error log */
$serialized = $serializable->serialize();
/**point of execution does not reach here */
$unserialized = $serializable->unserialize($serialized);
echo "finished!";
?>


Expected result:
----------------
return value equal to the object serialized using the serialize function.

Actual result:
--------------
Apache crashes with internal server error and a Premature end of script headers error.