PHP Replace Leading Zeros with Same Number of Spaces - php

Question

I'd like to replace a string like 0001 with " 1" with 3 spaces.
I've tried str_replace but that doesn't work on 0010.
I've tried some preg_replace but can't get the replacement right to replace the same number
I've written this basic thing and it works, but am looking for something more efficient if possible.
$pin = '0010';
$temp = ltrim($pin, '0');
$spaces = strlen($pin) - strlen($temp);
for ($x=1;$x<=$spaces;$x++) $temp = ' '.$temp;
echo $temp;
Closest I got with preg_replace was this but I'm not sure what to do with replacement:
preg_replace('/0+/', ' ', $pin)

Answer 1

\G for the win!
https://www.regular-expressions.info/continue.html
\G will match the start of the string and continue to match until it can't.
What is the use of '\G' anchor in regex?
Match a zero from the start of the string, then match every following zero one-at-a-time. Replace every matched zero with a space.
Code: (Demo)
$pin = '0010';
var_export(preg_replace('~\G0~', ' ', $pin));
Output:
' 10'

Answer 2

I don't see how to do this any easier with a regular expression, but you could make your other code more concise by using str_repeat:
$pin = '0010';
$temp = ltrim($pin, '0');
$spaces = strlen($pin) - strlen($temp);
$new_pin = str_repeat(' ', $spaces) . $temp;
echo $new_pin;

Answer 3

You said:
but am looking for something more efficient if possible
First, note that a one-liner isn't necessarily efficient(as you tried for preg_replace() and regex is actually a bit slower since it gets compiled first).
Second, you can better adopt for just a 2 pass approach over the string. This also edits the string in-place without extra string variables which is desirable in your case.
Snippet:
<?php
$str = '000010';
$len = strlen($str);
for($i = 0; $i < $len; ++$i){
if($str[$i] == '0'){
$str[$i] = ' ';
}else{
break;
}
}
echo $str;