Description:
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I stumbled upon strange behavior of php function function_exists(), when called on disabled function (in php.ini - disable_function). 

The thing is, that if I provide the function name parameter directly as string, the result is different than when provided as variable. When called first time, result is fine. But when the result is served by the OPCache, results are wrong.

Tested in clean build of PHP 5.6 and 5.7, with shipped OPCache (Zend OPcache v7.0.4-dev). In PHP 5.5, the results are correct.

PHP Build:
./configure --prefix=/usr/local/php/5.6.7-test

PHP config:
disable_functions = posix_getpwuid
date.timezone = Europe/Prague
zend_extension=/usr/local/php/5.6.7-test/lib/php/extensions/no-debug-non-zts-20131226/opcache.so

Test script:
---------------
<?
echo phpversion() . "\n";
$f='posix_getpwuid';
$r1=function_exists('posix_getpwuid');
$r2=function_exists($f);
echo "\n\n";

echo "string: ";
var_dump ($r1);
echo "var.  : ";
var_dump ($r2);

echo "opcache status: ";
var_dump(opcache_get_status()['opcache_enabled']);

Expected result:
----------------
This is the result of the first call, this is how it should be:

# /usr/local/php/php-TEST/bin/php-cgi -c /data/web/php-test/ fce.php

X-Powered-By: PHP/5.6.7
Content-type: text/html; charset=UTF-8

5.6.7

string: bool(false)     # <--- correct result
var.  : bool(false)
opcache status: bool(true)

Actual result:
--------------
Any subsequent call:

# /usr/local/php/php-TEST/bin/php-cgi -c /data/web/php-test/ fce.php

X-Powered-By: PHP/5.6.7
Content-type: text/html; charset=UTF-8

5.6.7

string: bool(true)     # <--- HERE IS THE ERROR
var.  : bool(false)
opcache status: bool(true)