Specify MDJsonEncodingFailedException for failure to encode JSON through

MD_STD::json_encode

exceptions/MDJsonEncodingFailedException.php

@@ -0,0 +1,19 @@
+<?PHP
+declare(strict_types = 1);
+
+/**
+ * Reports a failure to encode JSON data.
+ */
+final class MDJsonEncodingFailedException extends Exception {
+    /**
+     * Error message.
+     *
+     * @return string
+     */
+    public function errorMessage() {
+        //error message
+        $errorMsg = 'Failed to encode JSON data.';
+        return $errorMsg;
+
+    }
+}