Files

It’s time to look at long-term data stores. The most obvious one is the file system. The logic is simple—if we need to save some data, we put it into a file. That’s what computers do.

Working with files isn’t popular in web applications, but it remains a powerful tool for storing data and passing it between applications.

Using files in PHP

PHP offers many functions for working with files. The complete list is in the PHP Manual.

Here’s a list of the most commonly used functions.

Single operation functions

These are useful when performing a single operation on a file.

• The file_exists() function returns true if the requested file exists. If we want to read the file or write to it, it’s better to also check the permissions with the is_readable() or is_writable() functions. They return true if the file exists and the script has the necessary permissions for them.
• The file_get_contents() function reads the whole file into a string.
• The file() function reads the whole file as an array of strings, one string per line. The result still contains line endings.
• The file_put_contents() function saves a string into a file. By default, it overwrites the file. We can pass the FILE_APPEND flag as a third argument to append the string to the end of the file instead.
• The readfile() function passes the file

...