getting error while updating Composer

I have a project in Laravel-5.1 and I have changed my platform from win10 to Ubuntu.

Showing error:

Loading composer repositories with package information

Updating dependencies (including require-dev)

Your requirements could not be resolved to an installable set of packages.

  Problem 1
- laravel/framework v5.2.9 requires ext-mbstring * -> the requested PHP extension mbstring is missing from your system.
- laravel/framework v5.2.8 requires ext-mbstring * -> the requested PHP extension mbstring is missing from your system.
- laravel/framework v5.2.7 requires ext-mbstring * -> the requested PHP extension mbstring is missing from your system.
- laravel/framework v5.2.6 requires ext-mbstring * -> the requested PHP extension mbstring is missing from your system.
- laravel/framework v5.2.5 requires ext-mbstring * -> the requested PHP extension mbstring is missing from your system.
- laravel/framework v5.2.4 requires ext-mbstring * -> the requested PHP extension mbstring is missing from your system.
- laravel/framework v5.2.31 requires ext-mbstring * -> the requested PHP extension mbstring is missing from your system.
- laravel/framework v5.2.30 requires ext-mbstring * -> the requested PHP extension mbstring is missing from your system.
- laravel/framework v5.2.3 requires ext-mbstring * -> the requested PHP extension mbstring is missing from your system.
- laravel/framework v5.2.29 requires ext-mbstring * -> the requested PHP extension mbstring is missing from your system.
- laravel/framework v5.2.28 requires ext-mbstring * -> the requested PHP extension mbstring is missing from your system.
- laravel/framework v5.2.27 requires ext-mbstring * -> the requested PHP extension mbstring is missing from your system.
- laravel/framework v5.2.26 requires ext-mbstring * -> the requested PHP extension mbstring is missing from your system.
- laravel/framework v5.2.25 requires ext-mbstring * -> the requested PHP extension mbstring is missing from your system.
- laravel/framework v5.2.24 requires ext-mbstring * -> the requested PHP extension mbstring is missing from your system.
- laravel/framework v5.2.23 requires ext-mbstring * -> the requested PHP extension mbstring is missing from your system.
- laravel/framework v5.2.22 requires ext-mbstring * -> the requested PHP extension mbstring is missing from your system.
- laravel/framework v5.2.21 requires ext-mbstring * -> the requested PHP extension mbstring is missing from your system.
- laravel/framework v5.2.20 requires ext-mbstring * -> the requested PHP extension mbstring is missing from your system.
- laravel/framework v5.2.2 requires ext-mbstring * -> the requested PHP extension mbstring is missing from your system.
- laravel/framework v5.2.19 requires ext-mbstring * -> the requested PHP extension mbstring is missing from your system.
- laravel/framework v5.2.18 requires ext-mbstring * -> the requested PHP extension mbstring is missing from your system.
- laravel/framework v5.2.17 requires ext-mbstring * -> the requested PHP extension mbstring is missing from your system.
- laravel/framework v5.2.16 requires ext-mbstring * -> the requested PHP extension mbstring is missing from your system.
- laravel/framework v5.2.15 requires ext-mbstring * -> the requested PHP extension mbstring is missing from your system.
- laravel/framework v5.2.14 requires ext-mbstring * -> the requested PHP extension mbstring is missing from your system.
- laravel/framework v5.2.13 requires ext-mbstring * -> the requested PHP extension mbstring is missing from your system.
- laravel/framework v5.2.12 requires ext-mbstring * -> the requested PHP extension mbstring is missing from your system.
- laravel/framework v5.2.11 requires ext-mbstring * -> the requested PHP extension mbstring is missing from your system.
- laravel/framework v5.2.10 requires ext-mbstring * -> the requested PHP extension mbstring is missing from your system.
- laravel/framework v5.2.1 requires ext-mbstring * -> the requested PHP extension mbstring is missing from your system.
- laravel/framework v5.2.0 requires ext-mbstring * -> the requested PHP extension mbstring is missing from your system.
- laravel/framework v5.2.30 requires ext-mbstring * -> the requested PHP extension mbstring is missing from your system.
- Installation request for laravel/framework 5.2.* -> satisfiable by laravel/framework[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, v5.2.4, v5.2.5, v5.2.6, v5.2.7, v5.2.8, v5.2.9].

To enable extensions, verify that they are enabled in those .ini files:
- /etc/php/7.0/cli/php.ini
- /etc/php/7.0/cli/conf.d/10-mysqlnd.ini
- /etc/php/7.0/cli/conf.d/10-opcache.ini
- /etc/php/7.0/cli/conf.d/10-pdo.ini
- /etc/php/7.0/cli/conf.d/20-calendar.ini
- /etc/php/7.0/cli/conf.d/20-ctype.ini
- /etc/php/7.0/cli/conf.d/20-exif.ini
- /etc/php/7.0/cli/conf.d/20-fileinfo.ini
- /etc/php/7.0/cli/conf.d/20-ftp.ini
- /etc/php/7.0/cli/conf.d/20-gettext.ini
- /etc/php/7.0/cli/conf.d/20-iconv.ini
- /etc/php/7.0/cli/conf.d/20-json.ini
- /etc/php/7.0/cli/conf.d/20-mysqli.ini
- /etc/php/7.0/cli/conf.d/20-pdo_mysql.ini
- /etc/php/7.0/cli/conf.d/20-phar.ini
- /etc/php/7.0/cli/conf.d/20-posix.ini
- /etc/php/7.0/cli/conf.d/20-readline.ini
- /etc/php/7.0/cli/conf.d/20-shmop.ini
- /etc/php/7.0/cli/conf.d/20-sockets.ini
- /etc/php/7.0/cli/conf.d/20-sysvmsg.ini
- /etc/php/7.0/cli/conf.d/20-sysvsem.ini
- /etc/php/7.0/cli/conf.d/20-sysvshm.ini
- /etc/php/7.0/cli/conf.d/20-tokenizer.ini
You can also run `php --ini` inside terminal to see which files are used by PHP in CLI mode.

Composer/json.

{
"name": "laravel/laravel",
"description": "The Laravel Framework.",
"keywords": ["framework", "laravel"],
"license": "MIT",
"type": "project",
"require": {
  "php": ">=5.5.9",
  "laravel/framework": "5.2.*",
  "infyomlabs/laravel-generator": "dev-master",
  "laravelcollective/html": "5.2.*",
  "infyomlabs/core-templates": "dev-master",
  "infyomlabs/swagger-generator": "dev-master",
  "jlapp/swaggervel": "dev-master",
  "doctrine/dbal": "~2.3",
  "infyomlabs/generator-builder": "dev-master",
  "yajra/laravel-datatables-oracle": "~6.0",
  "barryvdh/laravel-ide-helper": "^2.1",
  "infyomlabs/adminlte-templates": "dev-master"
},
"require-dev": {
    "fzaninotto/faker": "~1.4",
    "mockery/mockery": "0.9.*",
    "phpunit/phpunit": "~4.0",
    "symfony/css-selector": "2.8.*|3.0.*",
    "symfony/dom-crawler": "2.8.*|3.0.*"
},
"autoload": {
    "classmap": [
        "database"
    ],
    "psr-4": {
        "App\\": "app/"
    }
},
"autoload-dev": {
    "classmap": [
        "tests/TestCase.php"
    ]
},
"scripts": {
    "post-root-package-install": [
        "php -r \"copy('.env.example', '.env');\""
    ],
    "post-create-project-cmd": [
        "php artisan key:generate"
    ],
    "post-install-cmd": [
        "Illuminate\\Foundation\\ComposerScripts::postInstall",
        "php artisan optimize"
    ],
    "post-update-cmd": [
        "Illuminate\\Foundation\\ComposerScripts::postUpdate",
        "php artisan optimize"
    ]
},
"config": {
    "preferred-install": "dist"
}

}

回答1:

Your error message is pretty explicit about what is going wrong:

laravel/framework v5.2.9 requires ext-mbstring * -> the requested PHP extension mbstring is missing from your system.

Do you have mbstring installed on your server and is it enabled?

You can install mbstring as part of the libapache2-mod-php5 package:

sudo apt-get install libapache2-mod-php5

Or standalone with:

sudo apt-get install php-mbstring

Installing it will also enable it, however you can also enable it by editing your php.ini file and remove the ; that is commenting it out if it is already installed.

If this is on your local machine, then follow the appropriate steps to install this on your environment.

回答2:

for php7 you can do that:

sudo apt-get install php-gd php-xml php7.0-mbstring

回答3:

In php7.2 Ubuntu 18.04 LTS

sudo apt-get install php-gd php-xml php7.2-mbstring

Works like a Charm

回答4:

A lot of good answers already for Ubuntu. I'm on Linux and had the same problem but none of the commands above worked for me.

With Linux and php70 I used the following command which worked great:

sudo yum install php70-mbstring -y

回答5:

After installing packages from given answers, i still get some errors then i install following package and it works fine:

php-xml

for specific version:

php7.0-xml

command for php 7.0

sudo apt-get install php7.0-xml

in some cases you also needs a package php7.0-common . install it same as above command.

回答6:

If you're using php 7.3 for laravel 5.7. this work for me

sudo apt-get install php-gd php-xml php7.3-mbstring