Description:
------------
Adding http proxy to default stream context making addressing different HTTPS domains in the same script impossible.
First request to HTTPS site after associating a http proxy sets ssl context to a single peer name and requests to any other domain will fail.

Tested with 7.1.6 and 5.6.30 on Windows and Ubuntu Linux.

Test script:
---------------
<?php

stream_context_set_default([
  "https" => [
    "proxy" => "tcp://proxy:3128"
    ],
]);
var_dump(stream_context_get_options(stream_context_get_default()));
file_get_contents("https://www.google.com/"); // fine
var_dump(stream_context_get_options(stream_context_get_default()));
file_get_contents("https://www.yahoo.com/"); // fine
var_dump(stream_context_get_options(stream_context_get_default()));
stream_context_set_default([
  "http" => [
    "proxy" => "tcp://proxy:3128"
    ],
]);
var_dump(stream_context_get_options(stream_context_get_default()));
file_get_contents("https://www.google.com/"); // fine
var_dump(stream_context_get_options(stream_context_get_default())); // ssl:peer_name is set
file_get_contents("https://www.yahoo.com/"); // Peer certificate CN=`*.www.yahoo.com' did not match expected CN=`www.google.com' in ...
var_dump(stream_context_get_options(stream_context_get_default()));


Expected result:
----------------
array(1) {
  ["https"]=>
  array(1) {
    ["proxy"]=>
    string(16) "tcp://proxy:3128"
  }
}
array(1) {
  ["https"]=>
  array(1) {
    ["proxy"]=>
    string(16) "tcp://proxy:3128"
  }
}
array(1) {
  ["https"]=>
  array(1) {
    ["proxy"]=>
    string(16) "tcp://proxy:3128"
  }
}
array(2) {
  ["https"]=>
  array(1) {
    ["proxy"]=>
    string(16) "tcp://proxy:3128"
  }
  ["http"]=>
  array(1) {
    ["proxy"]=>
    string(16) "tcp://proxy:3128"
  }
}
array(3) {
  ["https"]=>
  array(1) {
    ["proxy"]=>
    string(16) "tcp://proxy:3128"
  }
  ["http"]=>
  array(1) {
    ["proxy"]=>
    string(16) "tcp://proxy:3128"
  }
}
array(3) {
  ["https"]=>
  array(1) {
    ["proxy"]=>
    string(16) "tcp://proxy:3128"
  }
  ["http"]=>
  array(1) {
    ["proxy"]=>
    string(16) "tcp://proxy:3128"
  }
}


Actual result:
--------------
array(1) {
  ["https"]=>
  array(1) {
    ["proxy"]=>
    string(16) "tcp://proxy:3128"
  }
}
array(1) {
  ["https"]=>
  array(1) {
    ["proxy"]=>
    string(16) "tcp://proxy:3128"
  }
}
array(1) {
  ["https"]=>
  array(1) {
    ["proxy"]=>
    string(16) "tcp://proxy:3128"
  }
}
array(2) {
  ["https"]=>
  array(1) {
    ["proxy"]=>
    string(16) "tcp://proxy:3128"
  }
  ["http"]=>
  array(1) {
    ["proxy"]=>
    string(16) "tcp://proxy:3128"
  }
}
array(3) {
  ["https"]=>
  array(1) {
    ["proxy"]=>
    string(16) "tcp://proxy:3128"
  }
  ["http"]=>
  array(1) {
    ["proxy"]=>
    string(16) "tcp://proxy:3128"
  }
  ["ssl"]=>
  array(1) {
    ["peer_name"]=>
    string(14) "www.google.com"
  }
}
PHP Warning:  file_get_contents(): Peer certificate CN=`*.www.yahoo.com' did not match expected CN=`www.google.com' in test.php on line 21
PHP Warning:  file_get_contents(https://www.yahoo.com/): failed to open stream: Cannot connect to HTTPS server through proxy in test.php on line 21
array(3) {
  ["https"]=>
  array(1) {
    ["proxy"]=>
    string(16) "tcp://proxy:3128"
  }
  ["http"]=>
  array(1) {
    ["proxy"]=>
    string(16) "tcp://proxy:3128"
  }
  ["ssl"]=>
  array(1) {
    ["peer_name"]=>
    string(14) "www.google.com"
  }
}