=============================新的解決方法（較完善）=================================

    Composer 是 PHP5以上 的一個依賴管理工具。它允許你申明專案所依賴的程式碼庫，它會在你的專案中為你安裝他們。Composer 不是一個包管理器。是的，它涉及 "packages" 和 "libraries"，但它在每個專案的基礎上進行管理，在你專案的某個目錄中（例如 vendor）進行安裝。預設情況下它不會在全域性安裝任何東西。因此，這僅僅是一個依賴管理。

    安裝好Composer時通過composer install，發現沒有正常安裝，而是提示：

  [Composer\Exception\NoSslException]
  The openssl extension is required for SSL/TLS protection but is not available. If you can not enable the openssl extension, you can disable this error , at your own risk, by setting the 'disable-tls' option to true.

   對於這個問題，我嘗試使用下面的命令解決：

1. composer config -g -- disable-tls true  

    然而出現了另外的問題：
  [Composer\Downloader\TransportException]
  Your configuration does not allow connections to http://packagist.org/packages.json. See https://getcomposer.org/doc/06-config.md#secure-http for details.

    所以需要再次進行設定，禁用SSL

1. composer config secure-http false  
2.     composer config -g secure-http false  

    之後，一部分可以正常安裝了，還有一部分提示超過300stimeout，所以對時間進行設定：

    增加COMPOSER_PROCESS_TIMEOUT，通過命令composer config --list看到預設是300s，然後通過命令composer config -g process-timeout 600增加COMPOSER_PROCESS_TIMEOUT至600s。

    至此，Composer能夠正常執行。

================================================================

====Executing command 'composer update  "topthink/framework" --no-interaction --no-ansi'==== You are running composer with xdebug enabled. This has a major impact on runtime performance. See https://getcomposer.org/xdebug   [Composer\Exception\NoSslException]                                             The openssl extension is required for SSL/TLS protection but is not availab     le. If you can not enable the openssl extension, you can disable this error     , at your own risk, by setting the 'disable-tls' option to true.              update [--prefer-source] [--prefer-dist] [--dry-run] [--dev] [--no-dev] [--lock] [--no-custom-installers] [--no-autoloader] [--no-scripts] [--no-progress] [--no-suggest] [--with-dependencies] [-v|vv|vvv|--verbose] [-o|--optimize-autoloader] [-a|--classmap-authoritative] [--apcu-autoloader] [--ignore-platform-reqs] [--prefer-stable] [--prefer-lowest] [-i|--interactive] [--root-reqs] [--] [<packages>]... ====composer command completed with exit code 1====

解決方法：composer config -g -- disable-tls true

或者開啟php的ssl開啟

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來源:http://www.rabbit8.cn/576.html