How to access a file without losing data?

Question

PHP

How to access the file in order to read and rewrite data without loss.
Example: one script writes new values, the other reads and deletes, it is necessary that at the moment when they both process the file, the data is not lost. Since the second one can overwrite the data while the first one is adding them, something like this...

Answer 1

For this there is File locking
flock()
or

file_pit_contents('filename.txt', $my_data, LOCK_EX);

Answer 2

Use xml file.