Question

I know file_put_contents() makes it really easy to append data to a file in PHP. I’d like to try using PHP “threads” to file_put_contents() to the same log file from different PHP threads. Is there a risk in running file_put_contents() on the same file from different PHP threads or will these threads happily block if the file is locked or being accessed by another thread?

EDIT: Found a similar question that recommends flock(), but the risk question does not seem to be fully addressed. Are these “atomic” write operations?

Answer 1

as it says on the man page (that you gave a link for!):

// Write the contents to the file, 
// using the FILE_APPEND flag to append the content to the end of the file
// and the LOCK_EX flag to prevent anyone else writing to the file at the same time
file_put_contents($file, $person, FILE_APPEND | LOCK_EX);

Use the LOCK_EX flag to prevent double writes