PHP what happens when a string is double times mysqli_real_escape_string

[kennyg11]

I'm using mysqli.When I echo \[code\]mysqli_real_escape_string($db,mysqli_real_escape_string($db,'"'));\[/code\]which one of those will be the output:1. \[code\]\"\[/code\]2. \[code\]\\\"\[/code\]?Is there a safe way to check whether a string has been already escaped?Unfortunately, I cannot test at present as I cannot access MySQL for 24 hours.