PHP filesize() Function: Syntax, Parameters, Return Values, Examples, and Usage Tips

Function Prototype

<code>filesize(string $filename): int|false</code>

Parameter Description

$filename : required, the path to the file whose size is to be obtained.

Return Value

If successful, returns the file size in bytes.

If the operation fails, returns false .

Function Example

<code>$filename = 'path/to/file.txt';
$filesize = filesize($filename);
if ($filesize !== false) {
    echo "文件大小为：" . $filesize . " 字节";
} else {
    echo "无法获取文件大小";
}
</code>

Usage Notes

The file path must be a valid absolute or relative path.

If the file does not exist or is inaccessible, filesize() returns false .

The size is expressed in bytes.

If the file size exceeds PHP's integer limit (commonly 2 GB), filesize() may return a negative number.

Example Explanation

Assuming a file file.txt located at path/to/file.txt contains the text "Hello, World!" (13 bytes), the following code obtains and prints its size:

<code>$filename = 'path/to/file.txt'; // 文件路径
$filesize = filesize($filename); // 获取文件大小
if ($filesize !== false) {
    echo "文件大小为：" . $filesize . " 字节"; // 输出文件大小
} else {
    echo "无法获取文件大小"; // 输出错误信息
}
</code>

The output will be: "文件大小为：13 字节".

Extended Application

The filesize() function can also be used to determine whether a file is empty.

<code>$filename = 'path/to/empty.txt';
$filesize = filesize($filename);
if ($filesize === 0) {
    echo "文件为空";
} else {
    echo "文件不为空";
}
</code>

Summary

The filesize() function is a practical PHP utility for obtaining a file's size in bytes, enabling developers to handle files based on their size. However, when dealing with very large files, performance considerations may arise, and alternative methods might be preferable.