static int php_openssl_is_private_key(EVP_PKEY* pkey)
{
	assert(pkey != NULL);

	switch (EVP_PKEY_id(pkey)) {
#ifndef NO_RSA
		case EVP_PKEY_RSA:
		case EVP_PKEY_RSA2:
			{
				RSA *rsa = EVP_PKEY_get0_RSA(pkey);
				if (rsa != NULL) {
					const BIGNUM *p, *q;

					RSA_get0_factors(rsa, &p, &q);
					 if (p == NULL || q == NULL) {
						return 0;
					 }
				}
			}
			break;
#endif
#ifndef NO_DSA
		case EVP_PKEY_DSA:
		case EVP_PKEY_DSA1:
		case EVP_PKEY_DSA2:
		case EVP_PKEY_DSA3:
		case EVP_PKEY_DSA4:
			{
				DSA *dsa = EVP_PKEY_get0_DSA(pkey);
				if (dsa != NULL) {
					const BIGNUM *p, *q, *g, *pub_key, *priv_key;

					DSA_get0_pqg(dsa, &p, &q, &g);
					if (p == NULL || q == NULL) {
						return 0;
					}

					DSA_get0_key(dsa, &pub_key, &priv_key);
					if (priv_key == NULL) {
						return 0;
					}
				}
			}
			break;
#endif
#ifndef NO_DH
		case EVP_PKEY_DH:
			{
				DH *dh = EVP_PKEY_get0_DH(pkey);
				if (dh != NULL) {
					const BIGNUM *p, *q, *g, *pub_key, *priv_key;

					DH_get0_pqg(dh, &p, &q, &g);
					if (p == NULL) {
						return 0;
					}

					DH_get0_key(dh, &pub_key, &priv_key);
					if (priv_key == NULL) {
						return 0;
					}
				}
			}
			break;
#endif
#ifdef HAVE_EVP_PKEY_EC
		case EVP_PKEY_EC:
			{
				EC_KEY *ec = EVP_PKEY_get0_EC_KEY(pkey);
				if (ec != NULL && NULL == EC_KEY_get0_private_key(ec)) {
					return 0;
				}
			}
			break;
#endif
		default:
			php_error_docref(NULL, E_WARNING, "key type not supported in this PHP build!");
			break;
	}
	return 1;
}

The product does not check or incorrectly checks for unusual or exceptional conditions that are not expected to occur frequently during day to day operation of the product.