The 'or' Command in PHP Regular Expressions
In this lesson, we will break down the command
|, which is a more
powerful version of OR compared to
the command []. This command allows
you to split the regex into several parts.
The search term can match either one
part of the regex or another. Let's
look at some examples.
Example
In this example, the search pattern is: three
letters 'a' or three letters 'b':
<?php
$str = 'aaa bbb abb';
$res = preg_replace('#a{3}|b{3}#', '!', $str);
?>
As a result, the following will be written to the variable:
'! ! abb'
Example
In this example, the search pattern is: three
letters 'a' or from 1 and more
letters 'b':
<?php
$str = 'aaa bbb bbbb bbbbb axx';
$res = preg_replace('#a{3}|b+#', '!', $str);
?>
As a result, the following will be written to the variable:
'! ! ! ! axx'
Example
In this example, the search pattern is: one or more letters or three digits:
<?php
$str = 'a ab abc 1 12 123';
$res = preg_replace('#[a-z]+|\d{3}#', '!', $str);
?>
As a result, the following will be written to the variable:
'! ! ! 1 12 !'
Example
The vertical bar can divide the regex into not two parts, but any number of parts:
<?php
$str = 'aaa bbb ccc ddd';
$res = preg_replace('#a+|b+|c+#', '!', $str);
?>
As a result, the following will be written to the variable:
'! ! ! ddd'
Example
If the vertical bar is inside round
brackets, then 'or' works only inside
these brackets. For example, let's find strings
by the following pattern: at the beginning is
either 'a', or 'b' one or more
times, and then two letters 'x':
<?php
$str = 'axx bxx bbxx exx';
$res = preg_replace('#(a|b+)xx#', '!', $str);
?>
As a result, the following will be written to the variable:
'! ! ! exx'
Practice Tasks
Given a string:
<?php
$str = 'aeeea aeea aea axa axxa axxxa';
?>
Write a regex that will find strings
by the pattern: the edges are letters 'a',
and between them - either the letter 'e' any
number of times or the letter 'x' any
number of times.
Given a string:
<?php
$str = 'aeeea aeea aea axa axxa axxxa';
?>
Write a regex that will find strings
by the pattern: the edges are letters 'a',
and between them - either the letter 'e' two times
or the letter 'x' any number of times.
