C# SHA1 As PHP

public static string sha1(string input, bool rawOutput = false)
{
System.Text.UTF8Encoding encoder = new System.Text.UTF8Encoding();
System.Security.Cryptography.SHA1Managed hash =
new System.Security.Cryptography.SHA1Managed();
byte[] output = hash.ComputeHash(encoder.GetBytes(input));
return rawOutput ?
Convert.ToBase64String(output) :
BitConverter.ToString(output).Replace("-", "").ToLowerInvariant();
}