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hash_hmac_file() needs to read the content of the specified file to calculate the hash. If the file lacks read permissions, PHP will return an error or fail to execute correctly.
<span><span><span class="hljs-built_in">Warning</span></span><span>: hash_hmac_file() [</span><span><span class="hljs-keyword">function</span></span>.hash-hmac-file]: open_basedir restriction </span><span><span class="hljs-keyword">in</span></span><span> effect. File(/</span><span><span class="hljs-type">path</span></span><span>/</span><span><span class="hljs-keyword">to</span></span>/file) </span><span><span class="hljs-keyword">is</span></span><span> </span><span><span class="hljs-keyword">not</span></span><span> </span><span><span class="hljs-keyword">within</span></span><span> the allowed path(s)
</span></span>Ensure the file has correct read permissions. You can check the file permissions with the following command:
<span><span><span class="hljs-built_in">ls</span></span><span> -l /path/to/file
</span></span>If the file does not have read permissions, use chmod to update them:
<span><span><span class="hljs-built_in">chmod</span></span><span> 644 /path/to/file
</span></span>Additionally, if your code runs in a shared hosting environment or under open_basedir restrictions, make sure the file path is within the allowed directories. You may need to adjust this in php.ini or contact your system administrator.
open_basedir is a PHP security feature that restricts the file paths scripts can access. If a file is outside the allowed open_basedir paths, hash_hmac_file() cannot access it, resulting in an error.
<span><span><span class="hljs-built_in">Warning</span></span><span>: hash_hmac_file() [</span><span><span class="hljs-keyword">function</span></span>.hash-hmac-file]: open_basedir restriction </span><span><span class="hljs-keyword">in</span></span><span> effect. File(/</span><span><span class="hljs-type">path</span></span><span>/</span><span><span class="hljs-keyword">to</span></span>/file) </span><span><span class="hljs-keyword">is</span></span><span> </span><span><span class="hljs-keyword">not</span></span><span> </span><span><span class="hljs-keyword">within</span></span><span> the allowed path(s)
</span></span>Check the open_basedir setting in php.ini and ensure the file path is within the allowed directories.
If you are on shared hosting and cannot modify php.ini, try moving the file to an accessible directory or contact your hosting provider to adjust the open_basedir settings.
An incorrect file path is a common reason why hash_hmac_file() may fail. This can be caused by improperly configured relative or absolute paths.
<span><span><span class="hljs-built_in">Warning</span></span><span>: hash_hmac_file(/invalid/</span><span><span class="hljs-type">path</span></span>/</span><span><span class="hljs-keyword">to</span></span>/file): failed </span><span><span class="hljs-keyword">to</span></span> </span><span><span class="hljs-keyword">open</span></span> stream: </span><span><span class="hljs-keyword">No</span></span> such file </span><span><span class="hljs-keyword">or</span></span> directory
</span></span>Ensure the path passed to hash_hmac_file() is correct. If using a relative path, confirm that the current working directory (getcwd()) matches the file’s actual location.
Try using an absolute path to avoid path issues. For example:
<span><span><span class="hljs-variable">$file_path</span></span><span> = </span><span><span class="hljs-string">'/var/www/html/uploads/myfile.txt'</span></span><span>;
</span><span><span class="hljs-variable">$secret_key</span></span><span> = </span><span><span class="hljs-string">'your-secret-key'</span></span><span>;
</span><span><span class="hljs-variable">$hash</span></span><span> = </span><span><span class="hljs-title function_ invoke__">hash_hmac_file</span></span><span>(</span><span><span class="hljs-string">'sha256'</span></span><span>, </span><span><span class="hljs-variable">$file_path</span></span><span>, </span><span><span class="hljs-variable">$secret_key</span></span><span>);
</span></span>Before calling hash_hmac_file(), it’s best to confirm that the file exists. Calling hash_hmac_file() on a non-existent file will cause an error.
Use file_exists() to verify the file exists:
<span><span><span class="hljs-variable">$file_path</span></span><span> = </span><span><span class="hljs-string">'/path/to/file'</span></span><span>;
</span><span><span class="hljs-keyword">if</span></span><span> (</span><span><span class="hljs-title function_ invoke__">file_exists</span></span><span>(</span><span><span class="hljs-variable">$file_path</span></span><span>)) {
</span><span><span class="hljs-variable">$hash</span></span><span> = </span><span><span class="hljs-title function_ invoke__">hash_hmac_file</span></span><span>(</span><span><span class="hljs-string">'sha256'</span></span><span>, </span><span><span class="hljs-variable">$file_path</span></span><span>, </span><span><span class="hljs-variable">$secret_key</span></span><span>);
} </span><span><span class="hljs-keyword">else</span></span><span> {
</span><span><span class="hljs-keyword">echo</span></span><span> </span><span><span class="hljs-string">"File does not exist!"</span></span><span>;
}
</span></span>Beyond file permissions, the user running the PHP script (e.g., www-data) also needs read access to the file. If the PHP process lacks permission, hash_hmac_file() will fail.
Ensure the PHP process user has read access to the file. Check the PHP process user with:
<span><span>ps aux | grep php
</span></span>If the PHP process lacks permission, use chown to change the file owner to the PHP process user:
<span><span>sudo </span><span><span class="hljs-built_in">chown</span></span><span> www-data:www-data /path/to/file
</span></span>If unknown errors occur, enable PHP error reporting to help debug the issue. Add the following code at the top of your script to capture and display errors:
<span><span><span class="hljs-title function_ invoke__">ini_set</span></span><span>(</span><span><span class="hljs-string">'display_errors'</span></span><span>, </span><span><span class="hljs-number">1</span></span><span>);
</span><span><span class="hljs-title function_ invoke__">error_reporting</span></span><span>(E_ALL);
</span></span>With error reporting enabled, PHP will display detailed error information, helping you quickly identify the problem.
