Fix memory leak in php_openssl_pkey_from_zval()

Closes GH-16691.

NEWS

@@ -11,6 +11,7 @@ PHP                                                                        NEWS
 - OpenSSL:
   . Prevent unexpected array entry conversion when reading key. (nielsdos)
   . Fix various memory leaks related to openssl exports. (nielsdos)
+  . Fix memory leak in php_openssl_pkey_from_zval(). (nielsdos)
 
 - PDO:
   . Fixed memory leak of `setFetchMode()`. (SakiTakamachi)

ext/openssl/openssl.c

@@ -3533,6 +3533,7 @@ static EVP_PKEY *php_openssl_pkey_from_zval(
 		} else {
 			ZVAL_COPY(&tmp, zphrase);
 			if (!try_convert_to_string(&tmp)) {
+				zval_ptr_dtor(&tmp);
 				return NULL;
 			}
 

ext/openssl/tests/php_openssl_pkey_from_zval_leak.phpt

@@ -0,0 +1,23 @@
+--TEST--
+php_openssl_pkey_from_zval memory leak
+--EXTENSIONS--
+openssl
+--FILE--
+<?php
+
+class StrFail {
+    public function __toString(): string {
+        throw new Error('create a leak');
+    }
+}
+
+$key = ["", new StrFail];
+try {
+    openssl_pkey_export_to_file($key, "doesnotmatter");
+} catch (Error $e) {
+    echo $e->getMessage(), "\n";
+}
+
+?>
+--EXPECT--
+create a leak