add space in middle of string

[skyline]

I need to add a space after the 4th character in a string, how can i do this?

[stereofrog]

preg_replace('/^.{4}/', "$0 ", $str);

[skyline]

ok thanks

[trib4lmaniac]

Or

substr($str, 0, 4) . " " . substr($str, 4); 

[Jake Arkinstall]

Benchmark tests show that the substr method is nearly twice as fast as the preg_replace method

[skyline]

oh thanks, i'll try the faster approach then