Php format string with pattern

Question

I have a string (trimmed) and I would like to split this string according to a predefined pattern. I wrote a code which is probably more interpretive.

    $string="123456789";
    $format=['XXX','XX','XXXX'];
    $formatted="";
    foreach ($format as $cluster){
        $formattedCluster=substr($string,0,strlen($cluster));
        $string=substr($string,strlen($cluster));
        $formatted.=$formattedCluster.' ';
    }
    $formatted=substr($formatted, 0, -1);

    dd($formatted);

    //outputs: "123 45 6789"

As you can see it takes a string without any whitespace, and separates it with whitespaces according to a pattern $format in this case. The pattern is an array.

A pseudo example:

$str='qweasdzxc'

$pattern=['X','X','XXXX','XXX']

$formatted='q w easd zxc'; //expected output

It works as expected but it is rather hideous. What is the correct solution to this problem? By correctness, I mean speed and readability.

Environment: Php 7.4, Laravel 8

Answer 1

I would use https://www.php.net/manual/en/function.vsprintf.php do get the result:

$str='qweasdzxc';
$pattern='% % %%%% %%%'; // ['X','X','XXXX','XXX']
echo vsprintf(str_replace('%', '%s', $pattern), str_split($str));