At sign @ or Exclamation mark ! before PHP function - meaning

What is the meaning of At sign or Exclamation mark situated in front of PHP function ? For example, what will the functions @mail() or !strpos() do ?

Hi,

Both characters have a specific impact on the PHP function:

@ sign before PHP function - the presence of at sign will disable displaying of an errors. It suppresses error notifications even for errors that will terminate the script.

! mark before PHP function - the exclamation mark is a NOT operator in PHP, meaning it is used for logical negation. For example, the condition if(!strpos($string, $find)) { } is true, when value is not included in the string.