Composer accepts these flags as minimum-stability settings. The default setting for minimum-stability if not provided is assumed to be stable, but you could define any of the flags down the hierarchy.
–stable (most stable)
– RC
– beta
– alpha
– dev (least stable)
使用 @dev 解决版本问题
"minimum-stability": "stable",
"require": {
"php": ">=5.4.0",
"yiisoft/yii2": "*",
"yiisoft/yii2-bootstrap": "*",
"yiisoft/yii2-swiftmailer": "*",
"kartik-v/yii2-grid": "@dev"
},Setting composer minimum stability for your application
原文:http://www.cnblogs.com/yangyuqiu/p/6414005.html