注：以下技巧在composer2下面已经没必要了。！！！！！

升级成composer2吧，全解决了

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因为我一直用Yii2框架。所以安装composer和安装后需要执行的命令如下，【纯记录】

1、下载composer 
php -r "copy('https://getcomposer.org/installer', 'composer-setup.php');"
#php -r "if (hash_file('SHA384', 'composer-setup.php') === '544e09ee996cdf60ece3804abc52599c22b1f40f4323403c44d44fdfdd586475ca9813a858088ffbc1f233e9b180f061') { echo 'Installer verified'; } else { echo 'Installer corrupt'; unlink('composer-setup.php'); } echo PHP_EOL;"
php composer-setup.php
php -r "unlink('composer-setup.php');"
2、mv composer.phar /usr/local/bin/composer #移到系统目录，变成全局命令
3、composer config -g repo.packagist composer https://packagist.phpcomposer.com #国内源
phpcomposer好象垮了！
更新为：composer config -g repo.packagist composer https://packagist.laravel-china.org
4、composer global require hirak/prestissimo #多线程
5、composer global require "fxp/composer-asset-plugin:^1.4" #升级为1.4
6、composer update -vvv
就这样了
合并后的命令
php -r "copy('https://getcomposer.org/installer', 'composer-setup.php');"
php composer-setup.php
php -r "unlink('composer-setup.php');"
mv composer.phar /usr/local/bin/composer
composer config -g repo.packagist composer https://packagist.phpcomposer.com
composer global require hirak/prestissimo
composer global require "fxp/composer-asset-plugin:^1.4"
composer update -vvv
#over
如果采用了git，记得在运行完clone后：git config credential.helper store ，可以将当前用户名和密码存下来（针对HTTP方式，如果是ssh本来就不需要）