AES 256 GCM with php 5.6

Question

I have taken reference of code from this post : Trying to decrypt with aes-256-gcm with php

Code :

< ?php

    $textToEncrypt = "demo text";
    $password = '3sc3RLrpd17';
    $key = substr(hash('sha256', $password, true), 0, 32);
    $cipher = 'aes-256-gcm';
    $iv_len = openssl_cipher_iv_length($cipher);
    $tag_length = 16;
    $iv = openssl_random_pseudo_bytes($iv_len);

    
    $ciphertext = openssl_encrypt($textToEncrypt, $cipher, $key, OPENSSL_RAW_DATA, $iv);
    $encrypted = base64_encode($iv.$ciphertext);
    
    
    
    $textToDecrypt = $encrypted;
    $encrypted = base64_decode($textToDecrypt);
    $password = '3sc3RLrpd17';
    $key = substr(hash('sha256', $password, true), 0, 32);
    $cipher = 'aes-256-gcm';
    $iv_len = openssl_cipher_iv_length($cipher);
    $iv = substr($encrypted, 0, $iv_len);
    $ciphertext = substr($encrypted, $iv_len);
    $decrypted = openssl_decrypt($ciphertext, $cipher, $key, OPENSSL_RAW_DATA, $iv);
    var_dump (openssl_error_string());
    var_dump($decrypted);
    echo $decrypted;


?>

Running this code on PHP 5.6 Now the issue is I am always getting false as decrypted text.

What is wrong?