mmap() failed: [12] Cannot allocate memory

That is because PHP is running with a memory limit by default. You can by-pass it by running the following command

php -d memory_limit=-1 /usr/local/bin/composer install

Note: you might need to change the path to composer

Another option would be updating your php.ini files and setting the memory_limit = -1.

I've tried all this /usr/bin/php5.5-cli -d memory_limit=-1 composer.phar install

and updated my php.ini file and clearing cache and removing the composer.lock and clearing the cache

Server RAM was Low

Hi @boyjarv, It seems that you were running a Server with 512 MB RAM

I too once had this Problem with some specific version of PHP 7.3. But didn't remember the Solution I found out :-(

Try Googling

still not working, I updated server performance level 5 which gave me 768mb and 19gb max ram

Please help

Did you found the solution yet?? cause im facing the same problem.

Hi @hemantghatawal , this answer on Stackoverflow solved the issue on my end https://stackoverflow.com/a/55074773/7011672