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
	$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:

'! ! ! ! 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
	$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:

'xaz x1z ! x.z !'

Practice Tasks

Write a regex that will find strings by the pattern: digit or dot from 1 or more times.

Write a regex that will find strings by the pattern: not a digit and not a letter from 'a' to 'g' from 3 to 7 times.