我将我的laravel安装从我的远程服务器拉到我的本地计算机，现在想要执行“composer install＆＃39;安装所有必需的包。整个过程顺利进行。但是现在我收到了这个错误：
- laravel / framework v5.1.17需要symfony / dom-crawler 2.7。* - ＆gt; symfony / dom-crawler [2.7.x-dev，v2.7.0，v2.7.0-BETA1， v2.7.0-BETA2，v2.7.1，v2.7.10，v2.7.11，v2.7.12，v2.7.13，v2.7.14， v2.7.15，v2.7.16，v2.7.17，v2.7.18，v2.7.19，v2.7.2，v2.7.3，v2.7.4， v2.7.5，v2.7.6，v2.7.7，v2.7.8，v2.7.9]但这些与你的冲突 要求或最低稳定性。
我的composer.json看起来像这样：
> {
> "name": "laravel/laravel",
> "description": "The Laravel Framework.",
> "keywords": ["framework", "laravel"],
> "license": "MIT",
> "type": "project",
> "require": {
> "php": ">=5.5.9",
> "laravel/framework": "5.2.*",
> "league/fractal": "^0.12.0",
> "pda/pheanstalk": "^3.1",
> "witty/laravel-push-notification": "dev-master",
> "illuminate/html": "^5.0",
> "way/generators": "^3.0",
> "laracasts/generators": "^1.1"
> },
> "require-dev": {
> "fzaninotto/faker": "~1.4",
> "mockery/mockery": "0.9.*",
> "phpunit/phpunit": "~4.0",
> "phpspec/phpspec": "~2.1",
> "symfony/dom-crawler": "~3.0"
> },
> "autoload": {
> "classmap": [
> "database"
> ],
> "psr-4": {
> "App\\": "app/"
> }
> },
> "autoload-dev": {
> "classmap": [
> "tests/TestCase.php"
> ]
> },
> "scripts": {
> "post-install-cmd": [
> "php artisan clear-compiled",
> "php artisan optimize"
> ],
> "pre-update-cmd": [
> "php artisan clear-compiled"
> ],
> "post-update-cmd": [
> "php artisan optimize"
> ],
> "post-root-package-install": [
> "php -r \"copy('.env.example', '.env');\""
> ],
> "post-create-project-cmd": [
> "php artisan key:generate"
> ]
> },
> "config": {
> "preferred-install": "dist"
> } }
我还没有改变我的代码，只是干净地安装了我的电脑。
当我尝试更改为dom-crawler~2.7时出现此错误：
> Problem 1
> - Conclusion: don't install laravel/framework v5.2.45
> - Conclusion: don't install laravel/framework v5.2.44
> - Conclusion: don't install laravel/framework v5.2.43
> - Conclusion: don't install laravel/framework v5.2.42
> - Conclusion: don't install laravel/framework 5.2.41
> - Conclusion: don't install laravel/framework v5.2.40
> - Conclusion: don't install laravel/framework v5.2.39
> - Conclusion: don't install laravel/framework v5.2.38
> - Conclusion: don't install laravel/framework v5.2.37
> - Conclusion: don't install laravel/framework v5.2.36
> - Conclusion: don't install laravel/framework v5.2.35
> - Conclusion: don't install laravel/framework v5.2.34
> - Conclusion: don't install laravel/framework v5.2.33
> - Conclusion: don't install laravel/framework v5.2.32
> - Conclusion: don't install laravel/framework v5.2.31
> - Conclusion: don't install laravel/framework v5.2.30
> - Conclusion: don't install laravel/framework v5.2.29
> - Conclusion: don't install laravel/framework v5.2.28
> - Conclusion: don't install laravel/framework v5.2.27
> - Conclusion: don't install laravel/framework v5.2.26
> - Conclusion: don't install laravel/framework v5.2.25
> - Conclusion: don't install laravel/framework v5.2.24
> - Conclusion: don't install laravel/framework v5.2.23
> - Conclusion: don't install laravel/framework v5.2.22
> - Conclusion: don't install laravel/framework v5.2.21
> - Conclusion: don't install laravel/framework v5.2.20
> - Conclusion: don't install laravel/framework v5.2.19
> - Conclusion: don't install laravel/framework v5.2.18
> - Conclusion: don't install laravel/framework v5.2.17
> - Conclusion: don't install laravel/framework v5.2.16
> - Conclusion: don't install laravel/framework v5.2.15
> - Conclusion: don't install laravel/framework v5.2.14
> - Conclusion: don't install laravel/framework v5.2.13
> - Conclusion: don't install laravel/framework v5.2.12
> - Conclusion: don't install laravel/framework v5.2.11
> - Conclusion: don't install laravel/framework v5.2.10
> - Conclusion: don't install laravel/framework v5.2.9
> - Conclusion: don't install laravel/framework v5.2.8
> - Conclusion: don't install laravel/framework v5.2.7
> - Conclusion: don't install laravel/framework v5.2.6
> - Conclusion: don't install laravel/framework v5.2.5
> - Conclusion: don't install laravel/framework v5.2.4
> - Conclusion: don't install laravel/framework v5.2.3
> - Conclusion: don't install laravel/framework v5.2.2
> - Conclusion: don't install laravel/framework v5.2.1
> - witty/laravel-push-notification dev-master requires illuminate/support 5.0.* | 5.1.* -> satisfiable by
> laravel/framework[v5.1.17], illuminate/support[v5.0.0, v5.0.22,
> v5.0.25, v5.0.26, v5.0.28, v5.0.33, v5.0.4, v5.1.1, v5.1.13, v5.1.16,
> v5.1.2, v5.1.20, v5.1.22, v5.1.25, v5.1.28, v5.1.30, v5.1.31, v5.1.41,
> v5.1.6, v5.1.8].
> - witty/laravel-push-notification dev-master requires illuminate/support 5.0.* | 5.1.* -> satisfiable by
> laravel/framework[v5.1.17], illuminate/support[v5.0.0, v5.0.22,
> v5.0.25, v5.0.26, v5.0.28, v5.0.33, v5.0.4, v5.1.1, v5.1.13, v5.1.16,
> v5.1.2, v5.1.20, v5.1.22, v5.1.25, v5.1.28, v5.1.30, v5.1.31, v5.1.41,
> v5.1.6, v5.1.8].
> - Can only install one of: laravel/framework[v5.2.0, v5.1.17].
> - don't install illuminate/support v5.0.0|don't install laravel/framework v5.2.0
> - don't install illuminate/support v5.0.22|don't install laravel/framework v5.2.0
> - don't install illuminate/support v5.0.25|don't install laravel/framework v5.2.0
> - don't install illuminate/support v5.0.26|don't install laravel/framework v5.2.0
> - don't install illuminate/support v5.0.28|don't install laravel/framework v5.2.0
> - don't install illuminate/support v5.0.33|don't install laravel/framework v5.2.0
> - don't install illuminate/support v5.0.4|don't install laravel/framework v5.2.0
> - don't install illuminate/support v5.1.1|don't install laravel/framework v5.2.0
> - don't install illuminate/support v5.1.13|don't install laravel/framework v5.2.0
> - don't install illuminate/support v5.1.16|don't install laravel/framework v5.2.0
> - don't install illuminate/support v5.1.2|don't install laravel/framework v5.2.0
> - don't install illuminate/support v5.1.20|don't install laravel/framework v5.2.0
> - don't install illuminate/support v5.1.22|don't install laravel/framework v5.2.0
> - don't install illuminate/support v5.1.25|don't install laravel/framework v5.2.0
> - don't install illuminate/support v5.1.28|don't install laravel/framework v5.2.0
> - don't install illuminate/support v5.1.30|don't install laravel/framework v5.2.0
> - don't install illuminate/support v5.1.31|don't install laravel/framework v5.2.0
> - don't install illuminate/support v5.1.41|don't install laravel/framework v5.2.0
> - don't install illuminate/support v5.1.6|don't install laravel/framework v5.2.0
> - don't install illuminate/support v5.1.8|don't install laravel/framework v5.2.0
> - Installation request for laravel/framework 5.2.* -> satisfiable by laravel/framework[5.2.41, v5.2.0, v5.2.1, v5.2.10, v5.2.11,
> v5.2.12, v5.2.13, v5.2.14, v5.2.15, v5.2.16, v5.2.17, v5.2.18,
> v5.2.19, v5.2.2, v5.2.20, v5.2.21, v5.2.22, v5.2.23, v5.2.24, v5.2.25,
> v5.2.26, v5.2.27, v5.2.28, v5.2.29, v5.2.3, v5.2.30, v5.2.31, v5.2.32,
> v5.2.33, v5.2.34, v5.2.35, v5.2.36, v5.2.37, v5.2.38, v5.2.39, v5.2.4,
> v5.2.40, v5.2.42, v5.2.43, v5.2.44, v5.2.45, v5.2.5, v5.2.6, v5.2.7,
> v5.2.8, v5.2.9].
> - Installation request for witty/laravel-push-notification dev-master -> satisfiable by
> witty/laravel-push-notification[dev-master].
答案 0 :(得分：1)
库witty/laravel-push-notification太旧，无法在5.2版中安装Laravel。版本laravel-push-notification中illuminate/support的依赖关系之一是"5.0.* | 5.1.*"。
您正在尝试安装Laravel 5.2，但该库需要Laravel 5.1才能运行。
P.S。另外，下次尝试不删除composer.lock，有时可以保存项目。