How to make a personal algorithm for hash in PHP

Question

I want to make a personal algorithm for hashing texts in PHP. The letter 'a' crypt in 'xyz', 'b' in '256' and some more. How it's possible this?

Answer 1

It's possible by simple create a function that make characters substitution, like this:

function myEncrypt ($text)
{
    $text = str_replace(array('a', 'b'), array('xby', '256'), $text);
    // ... others

    return $text;
}

version with two arrays "search" and "replaceWith" passed as arguments:

function myEncrypt ($text, $search=array(), $replaceWith=array())
{
    return str_replace($search, $replaceWith, $text);   
}

WARNING: That way isn't a correct solution to encrypt a text, there are a lot of better ways to do a secure encryption with PHP (see for example this post).

Answer 2

I'm bored at work so I thought i'd give this a crack. This isn't secure at all. The crypt must be hard coded and the crypted character must have a size of 3.

<?php
//define our character->crypted text
$cryptArray = array( "a"=>"xyz","b"=>"256");
//This is our input
$string = "aab";

//Function to crypt the string
function cryptit($string,$cryptArray){    
    //create a temp string
    $temp = "";     
    //pull the length of the input
    $length = strlen($string);       
    //loop thru the characters of the input
    for($i=0; $i<$length; $i++){       
        //match our key inside the crypt array and store the contents in the temp array, this builds the crypted output
        $temp .= $cryptArray[$string[$i]];
    }
    //returns the string
    return $temp;

} 

//function to decrypt
function decryptit($string,$cryptArray){
    $temp = "";
    $length = strlen($string);    
    //Swap the keys with data
    $cryptArray = array_flip($cryptArray);     
    //since our character->crypt is count of 3 we must $i+3 to get the next set to decrypt
    for($i =0; $i<$length; $i = $i+3){       
        //read from the key
        $temp .= $cryptArray[$string[$i].$string[$i+1].$string[$i+2]];
    }
    return $temp;
}

$crypted =  cryptit($string,$cryptArray);
echo $crypted;

$decrypted = decryptit($crypted,$cryptArray);
echo $decrypted;     

The input was : aab

The output is:
xyzxyz256
aab

Here's the 3v4l link:
https://3v4l.org/chR2A