Description:
------------
Follow-up to https://bugs.php.net/bug.php?id=70861 which had the same problem.

./ext/mbstring/mb_gpc.c
./ext/pdo_firebird/firebird_statement.c
./ext/pdo_mysql/mysql_statement.c
./ext/pdo_sqlite/sqlite_statement.c
./ext/sqlite3/sqlite3.c
./ext/standard/image.c

all have code similar to:

  ZVAL_STR(parameter, php_stream_copy_to_mem(stm, PHP_STREAM_COPY_ALL, 0));

in various variations.

However php_stream_copy_to_mem() can return NULL, which will make this code fail under certain circumstances.

./ext/pdo/pdo_stmt.c has probably the best code for the problem to solve in a generic way:

                                        buf = php_stream_copy_to_mem((php_stream*)value, PHP_STREAM_COPY_ALL, 0);
                                        if (buf == NULL) {
                                                ZVAL_EMPTY_STRING(dest);
                                        } else {
                                                ZVAL_STR(dest, buf);
                                        }

and this likely should be made into a macro:

ZVAL_STR_OR_EMPTY(dest, buf, stream);

Expected result:
----------------
All functions should check the return value of php_stream_copy_to_mem()

Actual result:
--------------
Some function do not yet check the return value. This could lead to bugs.