How to put spaces in a string?

[callumd]

Let's say I have a string, that contains random numbers and letters:

$string = '12hd67dgbf40dkfgeqw647nkd873d73'; 

I would like to put spaces in this string after every 4th character, so that the sting would look like:

12hd 67dg bf40 dkfg eqw6 47nk d873 d73

The technique would need to work on strings of any length.

I have some ideas, but they're all pretty rough. I am guessing there must be some PHP function I could use to help me.

Any suggestions?

[callumd]

Got it:

$cc = '12345678901234567890';

$i=4;

while ((substr($cc, $i)) != NULL) {
    
    $cc = substr($cc, 0, $i) . ' ' . substr($cc, $i);
    
    $i = ($i + 5);
} 

[NogDog]

An alternative:

$cc = trim(chunk_split($cc, 4, ' '));