小马哥，我到第四步出现问题：
D:\>cd D:\wamp\www\yii\advanced

D:\wamp\www\yii\advanced>php -r "readfile('https://getcomposer.org/installer');"
 | php
PHP Warning:  readfile(): Unable to find the wrapper "https" - did you forget to
 enable it when you configured PHP? in Command line code on line 1
PHP Stack trace:
PHP   1. {main}() Command line code:0
PHP   2. readfile() Command line code:1
PHP Warning:  readfile(https://getcomposer.org/installer): failed to open stream
: Invalid argument in Command line code on line 1
PHP Stack trace:
PHP   1. {main}() Command line code:0
PHP   2. readfile() Command line code:1

Warning: readfile(): Unable to find the wrapper "https" - did you forget to enab
le it when you configured PHP? in Command line code on line 1

Call Stack:
    0.0020     117080   1. {main}() Command line code:0
    0.0020     117472   2. readfile() Command line code:1


Warning: readfile(https://getcomposer.org/installer): failed to open stream: Inv
alid argument in Command line code on line 1

Call Stack:
    0.0020     117080   1. {main}() Command line code:0
    0.0020     117472   2. readfile() Command line code:1


D:\wamp\www\yii\advanced>

不知道怎么回事，求助！