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PHP md5() Function

PHP String Reference Manual

Example

Calculate the MD5 hash of the string "Hello":

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

Definition and Usage

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

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

Explanation from RFC 1321 - MD5 Message-Digest Algorithm: The MD5 Message-Digest Algorithm takes an input and computes a 128-bit fingerprint or message digest that represents the input. The algorithm is designed for digital signature applications, where a large file is securely compressed before being encrypted in a public key system under a cryptographic scheme such as RSA.

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

The md5() function cannot handle arrays; arrays return null, md5(a[]) results in null.


Syntax

Parameter Description
string Required. The string to be calculated.
raw Optional. Specifies the output format: TRUE - Raw 16 character binary format<br> FALSE - Default. 32 character hexadecimal number

Technical Details

Return Value: Returns the computed MD5 hash on success, FALSE on failure.
PHP Version: 4+
--- ---
Changelog: The raw parameter became optional in PHP 5.0.
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More Examples

Example 1

Output the results 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>"; 
?>

Example 2

Output the results of md5() and test them:

<?php
$str = "Hello";
echo md5($str);

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

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