What does [Ss]* mean in regex in PHP?

The regular expression [\S\s]* in PHP means “don’t match new lines”.

In PHP, the /s flag can be used to make the dot match all the characters −

Example

 Live Demo

print(preg_match('/^[\S\s]$/s',"hello 
 world"));

Output

This will produce the following output −

0

The ‘preg_match’ function is used to match regular expression with the given input string. Here since the ‘\’ is encountered, it returns 0.