Why are requests to VK api not executed via Cron?

Question

PHP

There is a PHP code that, using the VK api, gets the number of friends of the desired user and makes an entry in the database.
The code works fine because I turn to the script through the browser and it does everything as it should.
I put the script in the list of cron tasks and realized that it does not fulfill requests to api vk, because. the line appears in the database, but the number of friends is 0.
Tell me how to solve the problem?

Answer 1

for cron, output errors to a file instead of /dev/null

Answer 2

Colleague, check if the code uses environment variables?
Look at the php errorlog