在不更改PHP版本的情况下更新composer

I try to update my composer but i get this error.

 Problem 1
- doctrine/instantiator 1.1.0 requires php ^7.1 -> your PHP version (7.0.10) does not satisfy that requirement.
- doctrine/instantiator 1.1.0 requires php ^7.1 -> your PHP version (7.0.10) does not satisfy that requirement.
- doctrine/instantiator 1.1.0 requires php ^7.1 -> your PHP version (7.0.10) does not satisfy that requirement.
- Installation request for doctrine/instantiator (locked at 1.1.0) -> satisfiable by doctrine/instantiator[1.1.0].

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How i can solve this problem without upgrade my version PHP ?

If you dont want to update your php version, just use this..

composer update --ignore-platform-reqs

or

composer install --ignore-platform-reqs

NOTES it is recommended to upgrade your version