src/Tokenizer/Token.php
public function isNativeConstant()
    {
        static $nativeConstantStrings = ['true', 'false', 'null'];

        return $this->isArray && \in_array(strtolower($this->content), $nativeConstantStrings, true);
    }
public function isNativeConstant()
    {
        static $nativeConstantStrings = ['true', 'false', 'null'];

        return $this->isArray && \in_array(strtolower($this->content), $nativeConstantStrings, true);
    }
Check if token is a native PHP constant: true, false or null.

@return bool