Reading Large Files

Imagine you are examining a server log to find the number of times a particular page is accessed. You could do this by counting the number of times the page URL appears in the log:

$data = file_get_contents(WEB_SERVER_LOG);

$num_of_page_loads = substr_count($data, 'https://www.mysite.com/mypage');

If your PHP application is running on a host with restricted resources, $data = file_get_contents(FILE_PATH); can cause your process to run out of memory and crash. A better way is to process your file line by line.

`fopen` And `fgets`

fopen and fgets are wrappers over functions in the C language that underlies PHP; they are simple but lightweight and easy to use.

fopen opens a file and returns a file pointer resource, a “handle” that other functions can use to refer to the file. The first parameter is the file path; the second is the type of access you need. 'r' is read only, starting from the beginning of the file.

fgets reads the next line from a “handle” and returns it, or false if there are no more lines.

fclose tidies up by closing the “handle”.

$file_handle = fopen(WEB_SERVER_LOG, 'r');

$num_of_page_loads = 0;
while ($line = fgets($file_handle)) {
    if (strpos($line, PAGE_URL) !== false) {
        $num_of_page_loads ++;
    }
}

fclose($file_handle);

This code will only read one line of the file at a time memory. Using these low level functions is an excellent way to ensure you code handles large inputs without using too much memory.

fopen And fgets

`fopen` And `fgets`