# PHP md5() Function

PHP String Reference

## Example

Calculate the MD5 hash of the string "Hello":

<?php
$str = "Hello";
echo md5($str);
?>
Run example »

## Definition and Usage

The md5() function calculates the MD5 hash of a string.

The md5() function uses the RSA Data Security, Inc. MD5 Message-Digest Algorithm.

From RFC 1321 - The MD5 Message-Digest Algorithm: "The MD5 message-digest algorithm takes as input a message of arbitrary length and produces as output a 128-bit "fingerprint" or "message digest" of the input. The MD5 algorithm is intended for digital signature applications, where a large file must be "compressed" in a secure manner before being encrypted with a private (secret) key under a public-key cryptosystem such as RSA."

To calculate the MD5 hash of a file, use the md5_file() function.

## Syntax

md5(string,raw)

Parameter | Description
--- | ---
string | Required. The string to be calculated

raw

Optional. Specifies hex or binary output format:

- TRUE - Raw 16 character binary format
- FALSE - Default. 32 character hex number

## Technical Details

Return Value: | Returns the calculated MD5 hash on success, or FALSE on failure
PHP Version: | 4+
Changelog: | The raw parameter became optional in PHP 5.0

## More Examples

## Example 1

Print the result of md5():

<?php
$str = "Hello";
echo "The string: ".$str."<br>";
echo "TRUE - Raw 16 character binary format: ".md5($str, TRUE)."<br>";
echo "FALSE - 32 character hex number: ".md5($str)."<br>";
?>
Run example »

## Example 2

Print the result of md5() and then test it:

<?php
$str = "Hello";
echo md5($str);
if (md5($str) == "8b1a9953c4611296a827abf8c47804d7")
{
echo "<br>Hello world!";
exit;
}
?>
Run example »

PHP String Reference

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