Intercept function calls from the global namespace

[lisachenko]

According to the official documentation http://www.php.net/manual/en/language.namespaces.rules.php there is a name resolution rule:

Inside namespace (say A\B), calls to unqualified functions are resolved at run-time. Here is how a call to function foo() is resolved:

It looks for a function from the current namespace: A\B\foo().
It tries to find and call the global function foo().

This rule can be used by Go! library to dynamically intercept global function calls in the namespaces. For example, if we want to intercept a function file_get_contents() in the application, we can create this function in the current namespace, so it will be used instead of global function.

[lisachenko]

Example of mocking usleep() function:

use Go\Aop\Framework\FunctionAroundInterceptor;
use Go\Aop\Framework\ReflectionFunctionInvocation;
use Go\Aop\Intercept\FunctionInvocation;


function usleep($microseconds)
{
    $interceptor = new FunctionAroundInterceptor(function (FunctionInvocation $invocation) {
        echo 'Hello!';
        return $invocation->proceed();
    });
    $joinpoint = new ReflectionFunctionInvocation('usleep', array($interceptor));
    return $joinpoint(array($microseconds));
}

[lisachenko]

Merged in 28e5e81