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Hàm md5() trong PHP

Hướng dẫn cách sử dụng hàm md5() trong lập trình PHP

Tác dụng của hàm md5()

The md5() function calculates the MD5 (Message Digest Algorithm 5) hash of a string.

This function calculates the MD5 hash of string using the RSA Data Security, Inc. MD5 Message-Digest Algorithm, and returns that hash. To calculate the MD5 hash of a file, use the md5_file() function.

The following table summarizes the technical details of this function.

Return Value: Returns the MD5 hash on success, or FALSE on failure.
Version: PHP 4+

Warning: Using the md5() function to secure passwords is not recommended, due to the fast nature of this hashing algorithm. Use the password_hash() function to hash passwords.


The basic syntax of the md5() function is given with:

md5(string, raw_format);

The following example shows the md5() function in action.

// Sample string
$str = "Sparrow";

// Calculating the hash
echo md5($str);


The md5() function accepts the following parameters.

Parameter Description
string Required. Specifies the input string.
raw_format Optional. If set to true, it returns the hash in raw binary format with a length of 16. Default value is false which returns the hash as a 32-character hexadecimal number.

More Examples

Here're some more examples showing how md5() function actually works:

The following example calculates the MD5 hash in different formats.

// Sample string
$str = "Sparrow";

// Calculating the hash
echo "MD5 hash as a 32-character hexadecimal number: ".md5($str)."<br>";
echo "MD5 hash in 16-character raw binary format: ".md5($str, TRUE);

The following example checks whether the two MD5 hashes are identical or not.

// Sample string
$str = "Sparrow";

// Test if two hashes are Identical
if(md5($str) === "ef5a30521df4c0dc7568844eefe7e7e3"){
    echo "Sparrows are very social and they live in flocks.";

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