docker-compose `/docker-entrypoint.sh: exec: line 24: require: not found`

Environment

• Ubuntu 18.04 LTS
• Docker Composer Container

Problem

run follow command.

docker-compose run composer require phpunit/phpunit

got error.

/docker-entrypoint.sh: exec: line 24: require: not found

How to solve it.

remove composer.json file.

$ rm ./composer.json 

and re-run. succeeded.

docker-compose run composer require phpunit/phpunit

Description.

when I run --help command, i got Execption Output.

$ docker-compose run composer --help


  [Seld\JsonLint\ParsingException]                                        
  "./composer.json" does not contain valid JSON                           
  Parse error on line 1:                                                  

  ^                                                                       
  Expected one of: 'STRING', 'NUMBER', 'NULL', 'TRUE', 'FALSE', '{', '['  

composer.json file is empty.

$ cat ./composer.json
$