Cannot sign anything with PHP openssl_sign?
Warning: openssl_sign() [function.openssl-sign]: supplied key param cannot be coerced into a private key in /.../pages/user/dkim.php on line 66
Cannot sign

$pkeyid = openssl_get_privatekey($open_SSL_priv);
if (openssl_sign($s, $signature, $pkeyid))
    return base64_encode($signature) ;
else
    die("Cannot sign") ;

$open_SSL_pub=<<<EOD
-----BEGIN PUBLIC KEY-----
MFwwDQYJKoZIhvcNAQEBBQADSwAwSAJBANDiE2+Xi/WnO+s120NiiJhNyIButVu6
zxqlVzz0wy2j4kQVUC4ZRZD80IY+4wIiX2YxKBZKGnd2TtPkcJ/ljkUCAwEAAQ==
-----END PUBLIC KEY-----
EOD;

$open_SSL_priv=<<<EOD
-----BEGIN RSA PRIVATE KEY-----
MIIBOgIBAAJBANDiE2+Xi/WnO+s120NiiJhNyIButVu6zxqlVzz0wy2j4kQVUC4Z
RZD80IY+4wIiX2YxKBZKGnd2TtPkcJ/ljkUCAwEAAQJAL151ZeMKHEU2c1qdRKS9
sTxCcc2pVwoAGVzRccNX16tfmCf8FjxuM3WmLdsPxYoHrwb1LFNxiNk1MXrxjH3R
6QIhAPB7edmcjH4bhMaJBztcbNE1VRCEi/bisAwiPPMq9/2nAiEA3lyc5+f6DEIJ
h1y6BWkdVULDSM+jpi1XiV/DevxuijMCIQCAEPGqHsF+4v7Jj+3HAgh9PU6otj2n
Y79nJtCYmvhoHwIgNDePaS4inApN7omp7WdXyhPZhBmulnGDYvEoGJN66d0CIHra
I2SvDkQ5CmrzkW5qPaE2oO7BSqAhRZxiYpZFb5CI
-----END RSA PRIVATE KEY-----
EOD;

<?php
$rsa = new Crypt_RSA();
$rsa->loadKey(file_get_contents('privatekey.txt'));
$rsa->setSignatureMode(CRYPT_RSA_SIGNATURE_PKCS1);
file_put_contents('signature.txt', $rsa->sign(file_get_contents('plaintext.txt')));
?>

openssl dgst -sha1 -prverify privatekey.txt -signature signature plaintext.txt