当使用Regex for for循环PHP时

Question

I need use Regex in loop PHP And I have Problem like below. when i write this code it's work fine :

$phone_number= '2222463';

for ($i=1; $i <= 9; $i++) {
  if((preg_match("/^[$i]{3}/", $phone_number))){
    return true;
   }
}

but below code not return true :

for ($i=1; $i <= 9; $i++) {
  if((preg_match("/^[$i]{$i}/", $phone_number))){
    return true;
   }
}

Note : {2}=={$i}

Answer 1

$i = 3;
echo "{3}", PHP_EOL, "{$i}";
// {3}
// 3

{$...} is part of the complex PHP string interpolation syntax, and {$i} is interpreted as one variable interpolation. You need to escape/double the brackets here:

"/^[$i]{{$i}}/"