Description:
------------
When opcache is enabled, unexpected results will occur when executed twice or more.

Test script:
---------------
<?php
function foo(){
	$ch=curl_init('example.com');
	curl_setopt($ch,CURLOPT_RETURNTRANSFER,false);
	ob_start();
	$data=curl_exec($ch);
	ob_end_clean();
	var_dump('out1',$data);
	if(true===$data){
		if(null===$data){
			var_dump('in1',$data);
		}
	}
	var_dump('out2',$data);
}
foo();


Expected result:
----------------
string(4) "out1"
bool(true)
string(4) "out2"
bool(true)

Actual result:
--------------
string(4) "out1"
bool(true)
string(3) "in1"
NULL
string(4) "out2"
bool(true)