Using hash_file() to Generate a File Hash in PHP

hash_file() generates a hash value for the contents of a given file using a specified algorithm.

The function takes three parameters: $algo (the hash algorithm name, e.g., "md5" or "sha256"), $filename (the path to the file, supporting fopen wrappers), and an optional $raw_output boolean that determines whether the result is raw binary data (TRUE) or a lowercase hexadecimal string (FALSE, default).

It is useful for constant‑time string comparisons to prevent timing attacks, such as verifying password hashes produced by crypt() .

Parameters

algo : name of the hash algorithm, e.g., "md5", "sha256", "haval160,4".

filename : path to the file to be hashed; fopen wrappers are supported.

raw_output : set to TRUE to get raw binary output, FALSE for a lowercase hex string.

Return value

If $raw_output is TRUE, the function returns the raw binary digest; otherwise it returns a lowercase hexadecimal string (e.g., 32‑character MD5 hash).

Example

<?php
/* Create a file to hash */
file_put_contents('example.txt', 'The quick brown fox jumped over the lazy dog.');
echo hash_file('md5', 'example.txt');
?>

Running the example outputs:

5c6ffbdd40d9556b73a21e63c3e0e904