PHP Deprecated: Array and string offset access syntax with curly braces is deprecated

src/Mail.php

@@ -374,7 +374,7 @@ class Mail
           $headersSplit[$i+1] = $headerBodySeparator;
         if ($h === "" || $h === "--")
           continue;
-        if ($h{0} === " " || $h{0} === "\t")
+        if ($h[0] === " " || $h[0] === "\t")
         {
           $prev .= $prevCR.$h;
           $prevCR = $headersSplit[$i+1];
@@ -952,7 +952,7 @@ class Mail
     $part = $this->sectionGet ($attachmentIDs[$number]);
     foreach ($part as $key=>$val)
     {
-      if ($key{0} === "_")
+      if ($key[0] === "_")
       {
         if ($key !== "_contentEML" && $key !== "_contentUTF" &&
             $key !== "_parentID" && $key !== "_headersArray" &&
@@ -1671,7 +1671,7 @@ class Mail
         $res["Content-Type"] = $key;
       else
       {
-        if ($val{0} === "'" || $val{0} === "\"")
+        if ($val[0] === "'" || $val[0] === "\"")
           $val = substr ($val, 1, -1);
         $res[trim ($key)] = $val;
       }