framework/log/Target.php
protected function getContextMessage()
    {
        $context = ArrayHelper::filter($GLOBALS, $this->logVars);
        foreach ($this->maskVars as $var) {
            if (ArrayHelper::getValue($context, $var) !== null) {
                ArrayHelper::setValue($context, $var, '***');
            }
        }
        $result = [];
        foreach ($context as $key => $value) {
            $result[] = "\${$key} = " . VarDumper::dumpAsString($value);
        }

        return implode("\n\n", $result);
    }
protected function getContextMessage()
    {
        $context = ArrayHelper::filter($GLOBALS, $this->logVars);
        foreach ($this->maskVars as $var) {
            if (ArrayHelper::getValue($context, $var) !== null) {
                ArrayHelper::setValue($context, $var, '***');
            }
        }
        $result = [];
        foreach ($context as $key => $value) {
            $result[] = "\${$key} = " . VarDumper::dumpAsString($value);
        }

        return implode("\n\n", $result);
    }
Generates the context information to be logged.
The default implementation will dump user information, system variables, etc.
@return string the context information. If an empty string, it means no context information.