PHP encrypt/decrypt an AES .NET encrypted password

Question

I have a C# .NET project that provides Encrypt and Decrypt methods using AES.

(I don't expect to win any awards (or upvotes) for the C# code you're about to see but in my humble defence, I was not responsible for it, I've just inherited it, I recognise some real problems with it, and I would be open to improving it under a separate SO question.)

public static string Encrypt(string PlainText)
    {
        string Password = "password replaced for this question";
        string Salt = "salt replaced for this question";
        string HashAlgorithm = "SHA1";
        int PasswordIterations = 2;
        string InitialVector = "iv replaced for this question";
        int KeySize = 256;

        if (string.IsNullOrEmpty(PlainText))
            return "";

        byte[] InitialVectorBytes = Encoding.ASCII.GetBytes(InitialVector);
        byte[] SaltValueBytes = Encoding.ASCII.GetBytes(Salt);
        byte[] PlainTextBytes = Encoding.UTF8.GetBytes(PlainText);

        PasswordDeriveBytes DerivedPassword = new PasswordDeriveBytes(Password, SaltValueBytes, HashAlgorithm, PasswordIterations);

        byte[] KeyBytes = DerivedPassword.GetBytes(KeySize / 8);

        RijndaelManaged SymmetricKey = new RijndaelManaged();

        SymmetricKey.Mode = CipherMode.CBC;

        byte[] CipherTextBytes = null;

        using (ICryptoTransform Encryptor = SymmetricKey.CreateEncryptor(KeyBytes, InitialVectorBytes))
        {
            using (MemoryStream MemStream = new MemoryStream())
            {
                using (CryptoStream CryptoStream = new CryptoStream(MemStream, Encryptor, CryptoStreamMode.Write))
                {
                    CryptoStream.Write(PlainTextBytes, 0, PlainTextBytes.Length);
                    CryptoStream.FlushFinalBlock();
                    CipherTextBytes = MemStream.ToArray();
                    MemStream.Close();
                    CryptoStream.Close();
                }
            }
        }

        SymmetricKey.Clear();
        return Convert.ToBase64String(CipherTextBytes);
    }

public static string Decrypt(string CipherText)
    {
        string Password = "password replaced for this question";
        string Salt = "salt replaced for this question";
        string HashAlgorithm = "SHA1";
        int PasswordIterations = 2;
        string InitialVector = "iv replaced for this question";
        int KeySize = 256;


        if (string.IsNullOrEmpty(CipherText))
            return "";
        try
        {
            byte[] InitialVectorBytes = Encoding.ASCII.GetBytes(InitialVector);
            byte[] SaltValueBytes = Encoding.ASCII.GetBytes(Salt);
            byte[] CipherTextBytes = Convert.FromBase64String(CipherText);

            PasswordDeriveBytes DerivedPassword = new PasswordDeriveBytes(Password, SaltValueBytes, HashAlgorithm, PasswordIterations);

            byte[] KeyBytes = DerivedPassword.GetBytes(KeySize / 8);

            RijndaelManaged SymmetricKey = new RijndaelManaged();

            SymmetricKey.Mode = CipherMode.CBC;

            byte[] PlainTextBytes = new byte[CipherTextBytes.Length];

            int ByteCount = 0;

            using (ICryptoTransform Decryptor = SymmetricKey.CreateDecryptor(KeyBytes, InitialVectorBytes))
            {
                using (MemoryStream MemStream = new MemoryStream(CipherTextBytes))
                {
                    using (CryptoStream CryptoStream = new CryptoStream(MemStream, Decryptor, CryptoStreamMode.Read))
                    {
                        ByteCount = CryptoStream.Read(PlainTextBytes, 0, PlainTextBytes.Length);
                        MemStream.Close();
                        CryptoStream.Close();
                    }
                }
            }

            SymmetricKey.Clear();
            return Encoding.UTF8.GetString(PlainTextBytes, 0, ByteCount);
        }
        catch
        {
            return "";
        }
    }

I need to perform equivalent encryption/decryption but in PHP 7, e.g. so that PHP can decrypt (to plain text) a string that was encrypted using the .NET Encrypt method, and encrypt a string in such a way that the .NET Decrypt function will return the plain text.

I know just enough about encryption to be dangerous, and not nearly enough to know how to do this "properly".