split string

[alirezaok]

hi

i have a variabale. it is number
i want to split each of 3 digits of it with comma form right side.

example

$test1=51345786;
echo $test1;

i want to show it as this: 51,345,786

anybody know how do i show as it?

[Weedpacket]

RTFM
[man]number_format[/man]