php - different ways to open a file

For many different technical reasons, PHP requires you to specify your intentions when you open a file. Below are the three basic ways to open a file and the corresponding character that PHP uses.

• Read: 'r'

Open a file for read only use. The file pointer begins at the front of the file.

• Write: 'w'

Open a file for write only use. In addition, the data in the file is erased and you will begin writing data at the beginning of the file. This is also called truncating a file, which we will talk about more in a later lesson. The file pointer begins at the start of the file.

• Append: 'a'

Open a file for write only use. However, the data in the file is preserved and you begin will writing data at the end of the file. The file pointer begins at the end of the file.

A file pointer is PHP's way of remembering its location in a file. When you open a file for reading, the file pointer begins at the start of the file. This makes sense because you will usually be reading data from the front of the file.

However, when you open a file for appending, the file pointer is at the end of the file, as you most likely will be appending data at the end of the file. When you use reading or writing functions they begin at the location specified by the file pointer.

php - file open: advanced

There are additional ways to open a file. Above we stated the standard ways to open a file. However, you can open a file in such a way that reading and writing is allowable! This combination is done by placing a plus sign "+" after the file mode character.

• Read/Write: 'r+'

Opens a file so that it can be read from and written to. The file pointer is at the beginning of the file.

• Write/Read: 'w+'

This is exactly the same as r+, except that it deletes all information in the file when the file is opened.

• Append: 'a+'

This is exactly the same as r+, except that the file pointer is at the end of the file.