Using SHA-256 for CodeIgniter hashing

CodeIgniter uses MD5 or SHA1 for its hashing:

$str = do_hash($str); // SHA1

$str = do_hash($str, 开发者_JAVA技巧'md5'); // MD5 

But, my project requires SHA-256. How would I resolve this?

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Can you not just call php's own hash()?

$str = hash ( "sha256", $str );