Question

I’m trying to replace all \n‘s sans that final one with \n\t in order to nicely indent for a recursive function.

This
that
then
thar
these
them

should become:

This
    that
    then
    thar
    these
them

This is what I have: preg_replace('/\n(.+?)\n/','\n\t$1\n',$var);

It currently spits this out:

This
    that
then
thar
these
them

Quick Overview:

Need to indent every line less the first and last line using regex, how can I accomplish this?

Answer 1

After fixing a quotes issue, your output is actually like this:

This
    that
then
    thar
these
them

Use a positive lookahead to stop that trailing \n from getting eaten by the search regex. Your “cursor” was already set beyond it so only every other line was being rewritten; your match “zones” overlapped.

echo preg_replace('/\n(.+?)(?=\n)/', "\n\t$1", $input);
//          newline-^  ^-text ^-lookahead ^- replacement

Live demo.