Master PHP’s filesize() Function: Quick Guide & Code Examples

Usage

The usage of filesize() is very simple. Below is its basic syntax: filesize(string $filename): int|false Here $filename specifies the path of the file whose size is to be retrieved. The function returns the file size in bytes, or false on failure.

Code Example

The following example demonstrates how to use filesize() to obtain a file’s size:

$filename = 'file.txt';

// Check if the file exists
if (file_exists($filename)) {
    $filesize = filesize($filename);
    echo '文件 ' . $filename . ' 的大小为 ' . $filesize . ' 字节。';
} else {
    echo '文件 ' . $filename . ' 不存在。';
}

The script first sets the file path, uses file_exists() to verify existence, then calls filesize() to get the size and prints it. If the file is missing, an error message is displayed.

Note: filesize() works only for local files; it cannot retrieve the size of remote files. To obtain remote file sizes, use cURL or send an HTTP HEAD request. The size is returned in bytes; you can convert it to KB, MB, etc., with simple arithmetic.

Conclusion

The filesize() function provides a straightforward way to obtain file size information in PHP, simplifying file‑handling tasks in backend development.