? PHP MD5 & SHA1 Functions

? Quick Overview

PHP provides hashing functions like md5() and sha1() to create fixed-length hash values from strings. These hashes are commonly used for data integrity checks, identifiers, and legacy systems.

? Key Concepts

md5() generates a 32-character hexadecimal hash
sha1() generates a 40-character hexadecimal hash
Hashes are one-way and cannot be reversed
Not suitable for secure password storage

? Syntax / Theory

string md5(string $data)
string sha1(string $data)
hash(string $algo, string $data)

? Example 1: Using md5()

? View Code Example

// Generate an MD5 hash from a password
<?php
$password = "mySecret123";
$hash = md5($password);
echo $hash;
?>

Explanation: The md5() function converts the string into a 32-character hexadecimal hash. MD5 is fast but insecure for password storage.

? Example 2: Using sha1()

? View Code Example

// Generate a SHA1 hash from a password
<?php
$password = "mySecret123";
$hash = sha1($password);
echo $hash;
?>

Explanation: sha1() produces a longer hash than MD5 but is still considered outdated for secure applications.

? Example 3: Using SHA-256

? View Code Example

// Generate a stronger SHA-256 hash
<?php
$password = "mySecret123";
$hash = hash("sha256", $password);
echo $hash;
?>

? Interactive Concept

Try hashing the same password using MD5, SHA1, and SHA-256. Notice how the length and complexity increase, improving resistance to brute-force attacks.

? Use Cases

File integrity checks
Legacy system compatibility
Checksum generation
Unique identifiers (non-sensitive)

✅ Tips & Best Practices

Avoid MD5 and SHA1 for passwords
Use password_hash() and password_verify()
Prefer SHA-256 or bcrypt for security

? Try It Yourself

Hash the same input with MD5, SHA1, and SHA-256
Compare hash lengths and formats
Experiment with password_hash()