Composer does not detect php7 instead it uses 5.6. How can I set the CLI to use php7

Question

Here when I execute php -v , it says it has php7

but when I try to execute composer update

the response it

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

  Problem 1
    - This package requires php >=7.0.0 but your PHP version (5.6.33) does not satisfy that requirement.

How can I fix this? NOTE : I'm not allowed to uninstall previous version of php

Here is the composer.json

{
    "name": "laravel/laravel",
    "description": "The Laravel Framework.",
    "keywords": ["framework", "laravel"],
    "license": "MIT",
    "type": "project",
    "require": {
        "php": ">=7.0.0",
        "fideloper/proxy": "~3.3",
        "intervention/image": "^2.4",
        "laravel/framework": "5.5.*",
        "laravel/passport": "^v1",
        "laravel/tinker": "~1.0"
    },
    "require-dev": {
        "filp/whoops": "~2.0",
        "fzaninotto/faker": "~1.4",
        "mockery/mockery": "0.9.*",
        "phpunit/phpunit": "~6.0"
    },
    "autoload": {
        "classmap": [
            "database/seeds",
            "database/factories"
        ],
        "psr-4": {
            "App\\": "app/"
        },
        "files": [
            "app/Helpers/misc.php"
        ]
    },
    "autoload-dev": {
        "psr-4": {
            "Tests\\": "tests/"
        }
    },
    "extra": {
        "laravel": {
            "dont-discover": [
            ]
        }
    },
    "scripts": {
        "post-root-package-install": [
            "@php -r \"file_exists('.env') || copy('.env.example', '.env');\""
        ],
        "post-create-project-cmd": [
            "@php artisan key:generate"
        ],
        "post-autoload-dump": [
            "Illuminate\\Foundation\\ComposerScripts::postAutoloadDump",
            "@php artisan package:discover"
        ]
    },
    "config": {
        "preferred-install": "dist",
        "sort-packages": true,
        "optimize-autoloader": true
    }
}

I already tried

composer update --ignore-platform-reqs

but I still I get another error, which is again related to the above problem.

Answer 1

As stated in the question you already have both the versions of PHP on your system, As Laravel uses the cli version you need to enable 7.X and disable 5.X.

You can achieve that by below commands

$ sudo a2dismod php5.6 // disable the loaded version
$ sudo a2enmod php7.0 // enable the desired version
$ sudo service apache2 restart // restart apache to get it in action

For More information You can install different version of PHP using the below commands

For Apache

$ sudo apt install php5.6   [PHP 5.6]
$ sudo apt install php7.0   [PHP 7.0]
$ sudo apt install php7.1   [PHP 7.1]

For Ngix

$ sudo apt install php5.6-fpm   [PHP 5.6]
$ sudo apt install php7.0-fpm   [PHP 7.0]
$ sudo apt install php7.1-fpm   [PHP 7.1]

To install any PHP modules, simply specify the PHP version and use the auto-completion functionality to view all modules as follows.

------------ press Tab key for auto-completion ------------ 
$ sudo apt install php5.6 
$ sudo apt install php7.0 
$ sudo apt install php7.1 

Now you can install most required PHP modules as per your requirements.

------------ Install PHP Modules ------------
$ sudo apt install php5.6-cli php5.6-xml php5.6-mysql 
$ sudo apt install php7.0-cli php7.0-xml php7.0-mysql 
$ sudo apt install php7.1-cli php7.1-xml php7.1-mysql