PHP encryption methods

MD5() - Genereate a hash string
E.g:

<?php
    $str= 'techsol99';
    echo md5($str);
?>
OP: bae06a769ecb6bbaa0e85370eff0458d

HASH_HMAC 
Generate a keyed hash value using the HMAC method
Ensures authentication between 2 parties while sending data over URL as query params.

E.g:
Lets say 2 parties A and B. A wants send data to B as url query params. Then A needs to be generated hash string with query params and send hash string along with query params.
When B recieves the query params then generate hash string with query params without hash value. After that compare with Newly generated hash string with query param hash string.

NOTE: salt should be shared by 2 parties.

A's code:

<?php
$queryString = 'subId=123&chapId=345';
$salt = 'techsol';
echo hash_hmac('sha256', $queryString, $salt, false); // Result: 688a864a96c1280bf118394e1d131edb9a4d09d3e2120cc78b92735b2ceff333
?>

URL : http://xyz.com?subId=123&chapId=345&key=688a864a96c1280bf118394e1d131edb9a4d09d3e2120cc78b92735b2ceff333

B's code:

<?php 
$urlQueryString = 'subId=123&chapId=345&key=688a864a96c1280bf118394e1d131edb9a4d09d3e2120cc78b92735b2ceff333';
parse_str($urlQueryString,$urlQueryArr);
$clientHash = $urlQueryArr['key'];
$pos = strpos($urlQueryString,'&key');
$queryString = substr($urlQueryString,0,$pos );
$salt = 'techsol';
$newHash = hash_hmac('sha256', $queryString, $salt, false);
if($clientHash != $newHash){
    echo "Data has tampered";
} else {
    echo "Not tampered";
}
?>

MCRYPT_DECRYPT:
NOTE: salt should be 16 char length.

    function encryptStr($plainText) {
        $salt = 'techsol99_php_me';
        return trim(base64_encode(mcrypt_encrypt(MCRYPT_RIJNDAEL_256, $salt, $plainText, MCRYPT_MODE_ECB, mcrypt_create_iv(mcrypt_get_iv_size(MCRYPT_RIJNDAEL_256, MCRYPT_MODE_ECB), MCRYPT_RAND))));
    }

    function decryptStr($encText) {
        $salt = 'techsol99_php_me';
        return trim(mcrypt_decrypt(MCRYPT_RIJNDAEL_256, $salt, base64_decode($encText), MCRYPT_MODE_ECB, mcrypt_create_iv(mcrypt_get_iv_size(MCRYPT_RIJNDAEL_256, MCRYPT_MODE_ECB), MCRYPT_RAND)));
    }

E.g:

$plainText = 'techsol99';

echo $encText = encryptStr($plainText);  OP: 0AHc0bAXOdP+XkaYpdoYcNmFvL9SVNugUiK4TIksPBE=
echo decryptStr($encText);   //OP: techsol99