PHP | hash_hmac_file() Function

Hello dear readers! welcome back to another edition of our tutorial on PHP. In this tutorial guide, we are going to be discussing about the PHP hash_hmac_file() Function.

The PHP hash_hmac_file() function is used for generating keyed hash value for the given file content by using HMAC method.

HMAC is an acronym which simply stands for keyed-hash message authentication code or hash-based message authentication code. It makes use of cryptographic hash function like md5, sha-256 and a secret key to hash the file contents given.

Syntax

Following below is the syntax to use this function -

hash_hmac_file ( 
   string $algo , string $filename , string $key [, bool $raw_output = FALSE ] 
) 
: string

READ: PHP | Hash Functions

Parameter Details

Sr.No	Parameter & Description
1	algo Name of the hashing algorithm. There is a big list of algorithm available with hash, some important ones are md5, sha256, etc. To get the full list of algorithms supported, check for hash_hmac_algos()
2	filename The filepath to get the file contents.
3	key Secret key to generate HMAC variant of the message digest.
4	raw_output By default the value is false and hence it returns lowercase hexits values. If the value is true, it will return raw binary data.

Return Value

This built-in PHP function returns a strings of calculated message digest that will be in the form of lowercase hexits if raw_output is false, otherwise it will return raw binary data.

PHP Version

This built-in function works from PHP version greater than 5.1.2.

Example1

The following below is an example which demonstrates the usage of hash_hmac_file() function -

<?php
   file_put_contents('file2.txt', 'Welcome to Webdesigntutorialz');
   echo hash_hmac_file('md5', 'file2.txt', 'anysecretkey');
?>

Output

When the above code is executed, it will produce the following result -

e9768f4407dcb22fb99cb6c4449f1067

Example2

The following example shows the difference in the hash_hmac_file() output when the file contents are changed -

<?php
   file_put_contents('abc.txt', 'Hello'); 
   echo hash_hmac_file('sha256', 'abc.txt', 'mysecretkey'); 
   echo "<br/><br/>";
   file_put_contents('abc.txt', 'World');
   echo hash_hmac_file('md5', 'abc.txt', 'anysecretkey'); 
?>

Output

When the above code is executed, it will produce the following result -

362a60a6ef4e35f9559304a6b5372b070c97ba33cb4a747503c9c58b5c85e6db2652fb7ccf4cff91df4f08add44b93b2

Example3

The following example shows the difference in PHP hash_file() and hash_hmac_file() output -

<?php
   file_put_contents('filetest.txt', 'Welcome to Webdesigntutorialz');
   echo hash_file('sha256', 'filetest.txt');
   echo "<br/><br/>";
   file_put_contents('abc.txt', 'Welcome to Webdesigntutorialz'); 
   echo hash_hmac_file('sha256', 'abc.txt', 'mysecretkey'); 
?>

Output

When the above code is executed, it will produce the following result -

b952e8666ddb57f4b80a70041a9bc151166dd11d4aaf1393c243cf720841be77<br/><br/>b6f6f03642e61cc076d4e2def5db4048c4bb2be8308a76190e346831a6301508

READ: PHP | hash() Function

Alright guys! This is where we are rounding up for this tutorial post. In our next tutorial, we will discuss about the hash_pbkdf2() Function in PHP.

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