lib/mail/Mail.php
public function addGlobalSubstitution($key, $value = null)
    {
        if ($key instanceof Substitution) {
            $substitution = $key;
            $this->substitutions[$substitution->getKey()]
                = $substitution->getValue();
            return;
        }
        $this->substitutions[$key] = $value;
    }
public function addGlobalSubstitution($key, $value = null)
    {
        if ($key instanceof Substitution) {
            $substitution = $key;
            $this->substitutions[$substitution->getKey()]
                = $substitution->getValue();
            return;
        }
        $this->substitutions[$key] = $value;
    }
public function addGlobalSubstitution ( $ key , $ value = null ) { if ( $ key instanceof Substitution ) { $ substitution = $ key ; $ this -> substitutions [ $ substitution -> getKey ( ) ] = $ substitution -> getValue ( ) ; return ; } $ this -> substitutions [ $ key ] = $ value ; }
Add a substitution to a Mail object

Note that substitutions added to Personalization objects override
global substitutions.

@param string|Substitution $key Key or Substitution object
@param string|null $value Value
Add a substitution to a Mail object