PHP function to escape regular expression characters

$str = preg_quote( " /d{3}(-d{4})/ " );
echo $str;
?>

Results : /\d{3}(\-\d{4})/

Example 2,

$str = preg_quote( " /d{3}(-d{4})/ " , " 3 " );
echo $str;
?>

Results: /\d{3}(\-\d{4})/

The main difference between the above two examples: It’s the “3” in the red area. In the second example, “3” is also escaped.