src/lexer/comments.js
function() {
    let ch = this.input();
    let token = this.tok.T_COMMENT;
    if (ch === "*") {
      // started with '/*' , check is next is '*'
      ch = this.input();
      if (this.is_WHITESPACE()) {
        // check if next is WHITESPACE
        token = this.tok.T_DOC_COMMENT;
      }
      if (ch === "/") {
        return token;
      } else {
        this.unput(1); // reset
      }
    }
    while (this.offset < this.size) {
      ch = this.input();
      if (ch === "*" && this._input[this.offset] === "/") {
        this.input();
        break;
      }
    }
    return token;
  }
function() {
    let ch = this.input();
    let token = this.tok.T_COMMENT;
    if (ch === "*") {
      // started with '/*' , check is next is '*'
      ch = this.input();
      if (this.is_WHITESPACE()) {
        // check if next is WHITESPACE
        token = this.tok.T_DOC_COMMENT;
      }
      if (ch === "/") {
        return token;
      } else {
        this.unput(1); // reset
      }
    }
    while (this.offset < this.size) {
      ch = this.input();
      if (ch === "*" && this._input[this.offset] === "/") {
        this.input();
        break;
      }
    }
    return token;
  }
Behaviour : https://github.com/php/php-src/blob/master/Zend/zend_language_scanner.l#L1927