Correct way to read files with PHP

Learn how to use PHP’s various file functions. Review basic file functions such as fopen, fclose, and feof; learn about read functions such as fgets, fgetss, and fscanf. And found functions that process entire files in one or two lines of code.

Let’s count how many ways there are

One of the joys of working with a modern programming language like PHP is the sheer number of options available. PHP easily wins Perl's motto "There's more than one way to do it" (not just one way to do it), especially when it comes to file handling. But with so many options available, which one is the best tool for the job? Of course, the actual answer depends on your goals for parsing the file, so it's worth taking the time to explore all options.


The traditional fopen method

The fopen method is probably the most familiar to former C and C++ programmers, because if you've used those languages, they're more or less tools you've had at your disposal for years. For either of these methods, the file is opened by the standard method of using fopen (the function used to read data), and then closed using fclose, as shown in Listing 1.

Listing 1. Use fgets to open and read files                        
$file_handle = fopen("myfile", "r");
while (!feof($file_handle)) {
 $line = fgets($file_handle);
 echo $line;
}
fclose($file_handle);

While most programmers with years of programming experience are familiar with these functions, let me break them down. Effectively follow these steps:
Open the file. $file_handle stores a reference to the file itself.
Check if you have reached the end of the file.
Continue reading the file until the end of the file is reached, printing each line as it is read.
Close the file.

With these steps in mind, I will review every file function used here.

fopen

fopen function will create a connection to a file. The reason I say "create a connection" is because in addition to opening a file, fopen can also open a URL: $fh = fopen("http://127.0.0.1/", "r");

This line of code will create a connection to the above page and allow you to start reading it as if it were a local file.

Note: The "r" used in fopen will instruct the file to be opened read-only. Since writing data to a file is outside the scope of this article, I won't list all other options. However, if reading from a binary file for cross-platform compatibility, "r" should be changed to "rb". You'll see an example of this later.

feof

feof command will detect if you have reached the end of the file and return True or False. The loop in Listing 1 continues until you reach the end of the file "myfile". Note: feof will also return False if a URL is being read and the socket times out because there is no more data to read.

fclose

Skipping forward to the end of Listing 1, fclose will do the opposite of fopen: it will close the connection to a file or URL. After executing this function, you will no longer be able to read any information from the file or socket.

fgets

Jump back a few lines in Listing 1 and you get to the heart of file processing: actually reading the file. The fgets function is the weapon of choice for the first example. It will extract a row of data from the file and return it as a string. After that, you can print or otherwise manipulate the data. The example in Listing 1 will print the entire file fine.

If you decide to limit the size of the processing data chunks, you can add a parameter to fgets to limit the maximum row length. For example, use the following code to limit the line length to 80 characters: $string = fgets($file_handle, 81);

Recall the "Note: The examples for this function already use slightly different parameters than fopen. When working with binary data, always remember to include the b option to fopen. If you skip this point, Microsoft® Windows® systems may not handle the file correctly because they handle new lines differently. If you're dealing with a Linux® system (or some other UNIX® variant), this may not seem to matter. But even if you're not developing for Windows, doing so will result in good cross-platform maintainability and is a good practice to follow.

The above code will read 4,096 bytes (4 KB) of data. Note: No matter how many bytes are specified, fread will never read more than 8,192 bytes (8 KB).

Assuming the file size is no more than 8 KB, the following code should be able to read the entire file into a string. $fh = fopen("myfile", "rb");
$data = fread($fh, filesize("myfile"));
fclose($fh);

If the file length is greater than this value, you can only Use a loop to read the rest in.

fscanf

Back to string processing, fscanf also follows the traditional C file library function. If you're not familiar with it, fscanf reads field data from a file into variables. list ($field1, $field2, $field3) = fscanf($fh, "%s %s %s");

The format string used by this function is described in many places (such as PHP.net), Therefore, we won’t go into details here. Suffice to say, string formatting is extremely flexible. It is worth noting that all fields are placed in the return value of the function. (In C, they are all passed as arguments.)

fgetss

fgetss functions differ from traditional file functions and give you a better understanding of the power of PHP. This function functions like the fgets function, but will strip any HTML or PHP tags found, leaving only plain text. View the HTML file shown below.

List 2. Sample HTML file                                                                                                           If you understand what "Cause there ain't no one for to give you no pain"
                means then you listen to too much of the band America