Character Groups Inside Square Brackets in PHP

Character groups \d, \D, \w, \W, \s, \S inside [] will denote exactly groups, that is, they will still be commands.

Example

In this example, the search pattern looks like this: between x's any digit, or a letter from 'a' to 'f':

php<?php
  $str = 'xax xbx x1x x2x xhx x@x';
  $res = preg_replace('#x[\da-f]x#', '!', $str);
?>

As a result, the following will be written to the variable:

php'! ! ! ! xhx x@x'

Example

In this example, the search pattern looks like this: letter 'x', then not a digit, not a dot, and not a lowercase Latin letter, then letter 'z':

php<?php
  $str = 'xaz x1z xAz x.z x@z';
  $res = preg_replace('#x[^\d.a-z]z#', '!', $str);
?>

As a result, the following will be written to the variable:

php'xaz x1z ! x.z !'

Practice Tasks