How does an nginx log output a variable?

The code is php and runs on nginx. one part of the code is the Mail function. to facilitate debugging, I want to output a variable, but I don't know where to output it. how can I output it? Node can directly console. log (), but how does php output on nginx? On the Internet, the logformat is changed, and the echo... code is php and runs on nginx. some of them use the mail function.
To facilitate debugging and output a variable,
But I don't know where to output it. how can I output it?
Node can directly console. log (), but how does php output on nginx?
Log format is changed on the internet. is echo used?
I don't quite understand. Is it possible to directly echo? Where is the output?
Please give us some advice,

Reply content:

The code is php and runs on nginx. part of the code is the Mail function.
To facilitate debugging and output a variable,
But I don't know where to output it. how can I output it?
Node can directly console. log (), but how does php output on nginx?
Log format is changed on the internet. is echo used?
I don't quite understand. Is it possible to directly echo? Where is the output?
Please give us some advice,

If nginx logs are not output using php, you should modify the nginx/conf/ngnix. conf file.
Change the format after log_format. you can see that different parameters correspond to different values.