Checking a String Character in PHP

Let there be a given string consisting of digits:

php<?php
  $str = '12345';
?>

Let's check if the first character of this string is equal to the number 1:

php<?php
  $str = '12345';
  
  if ($str[0] == 1) {
    echo '!';
  }
?>

Now let's check if the last character is equal to the number 5:

php<?php
  $str = '12345';
  $last = $str[-1];
  
  if ($last == 5) {
    echo '!';
  }
?>