PHP md5() Function

The PHP md5() function calculates the MD5 hash of string using the RSA Data Security, Inc. MD5 Message-Digest Algorithm, and returns that hash.

From RFC 1321: 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.

Note: It is not recommended to use this function to secure passwords, due to the fast nature of this hashing algorithm.

Syntax

md5(string, binary)

Parameters

`string`	`Required.` Specify the input string.
`binary`	`Optional.` If set to true, then the MD5 digest is returned in raw binary format with a length of 16, otherwise the returned value is a 32-character hexadecimal number. Default is false.

Return Value

Returns the MD5 hash as a string.

Example:

The example below illustrates on md5() function.

<?php
$str = "Hello";

echo "The string is: $str \n";
echo "The hash of string is: \n";
echo md5($str);
?>

The output of the above code will be:

The string is: Hello 
The hash of string is: 
8b1a9953c4611296a827abf8c47804d7

Example:

Consider one more example where optional parameter is used to calculate the hash of the string in different formats.

<?php
$str = "Hello";

echo "16 character binary format:\n";
echo md5($str, true);
echo "\n32 character hexadecimal number: \n";
echo md5($str);
?>

The output of the above code will be:

16 character binary format:
SÄa¨'«øÄx×
32 character hexadecimal number: 
8b1a9953c4611296a827abf8c47804d7

❮ PHP String Reference