preg_replace用后缀加上自身替换前缀

Question

I have a list of mobile phone $numbers and i have to change them, prefixing the number 39, if the number itself starts with one in $prefixes array.

I don't now how to back referencing to the found prefix, or (it's the same) how to get the matched prefix). I've tried the following but it's not working:

$numbers  = array('3284121532', '3478795687'); // the subject
$prefixes = array('328', '347');               // (will be) the pattern

// Build regex for each element of $prefix array
$pattern = array_map(function($s) { return "/^$s/"; }, $prefixes);
$replace = "39\{$1}";

var_dump(preg_replace($pattern, $replace, $numbers);

Any help would be appreciated, thanks.

Answer 1

$numbers  = array(3284121532, 3478795687);
$prefixes = implode('|',array(328, 347));

$numbers = array_map(function($n) use ($prefixes) {
    return preg_replace("/^($prefixes)/", '39$1', $n);
}, $numbers);

print_r($numbers);

The above will output

Array
(
    [0] => 393284121532
    [1] => 393478795687
)