lib/mail/Mail.php
public function addGlobalCustomArg($key, $value = null)
    {
        if ($key instanceof CustomArg) {
            $custom_arg = $key;
            $this->custom_args[$custom_arg->getKey()]
                = $custom_arg->getValue();
            return;
        }
        $this->custom_args[$key] = (string)$value;
    }
public function addGlobalCustomArg($key, $value = null)
    {
        if ($key instanceof CustomArg) {
            $custom_arg = $key;
            $this->custom_args[$custom_arg->getKey()]
                = $custom_arg->getValue();
            return;
        }
        $this->custom_args[$key] = (string)$value;
    }
public function addGlobalCustomArg ( $ key , $ value = null ) { if ( $ key instanceof CustomArg ) { $ custom_arg = $ key ; $ this -> custom_args [ $ custom_arg -> getKey ( ) ] = $ custom_arg -> getValue ( ) ; return ; } $ this -> custom_args [ $ key ] = ( string ) $ value ; }
Add a custom arg to a Mail object

Note that custom args added to Personalization objects override
global custom args.

@param string|CustomArg $key Key or CustomArg object
@param string|null $value Value
Add a custom arg to a Mail object