The modern concept of the file system is focused on speed, efficiency and comfort for the developer. Many people remember the times when it was necessary to waste time and lines of code. Open a file, organize the read/write process, control the data exchange process, track problems, and close the file properly. It's all history now.
As a sign of memory of the past, many languages have retained the classic operations for organizing the processes of writing/reading data, but offer much more efficient tools. In particular, the PHP file_put_contens() function is all at once: convenient, fast, practical.
Data line and file
In fact, it doesn't matter where the data is located. It must be stored in any process in any situation. A string is usually RAM, and a file is an external drive. A string cannot stay in memory forever, but a file is always saved.
The properties and purpose of PHP's file_put_contents() function are obvious: transforming a row from active to passive: transferring data from online control to storage.

The logic of modernprogramming is extremely simple in terms of data usage. Everything active and relevant in RAM is available instantly. Everything that you may need is stored on disk, in the cloud, or on any other storage device in a file. What a file is, where it is located, how it is arranged - the developer is not interested. It is important that a string can always be quickly placed in a file. It is of great importance that the line can always be extracted from the file and it will be the same as it was written.
Syntax of the PHP function file_put_contents()
The function has two parameters: where to write and what to write. The filename and data string are the two essential values of the write function. You can use the third - flags and the fourth parameter - resource context.
int file_put_contents(str.filename, str.data [, int flags [, resource context])
File name (str.filename) is the path and file name. If the path is not specified, the recording will be made at the location of the script or in the current folder. The data to write (str.data) is a string. You can use the file name, which is not entirely correct, because first PHP will implode and merge all the elements of the array into a string, and then it will write.

When using PHP's file_put_contents() function, it's best to define what gets written instead of forcing the programming language to take part in writing. The developer must control the data and processes himself, trusting the language only for simple and obvious actions.
Logic of modern file operations
Progress intechnically and reliability of file systems is too noticeable. Everything is working. The developer can count on the unconditional reliability of hardware and software.

The foregoing does not mean failure to take action against technical failures, malicious code and the likely actions of intruders. The code must be stable and secure - this is the rule of a professional developer.
Regarding strings and files: there can't be situations where PHP's file_put_contents() function doesn't work. Modern technologies are not perfect, but they function stably and reliably.
For a good result, it is enough to control what needs to be written, that is, the content of the line. You need to know exactly where the write will be done and how to read it back.
By using PHP's file_put_contents() function, the developer can be sure that the data string is stored and can always be read as written.