PHP 8.1.0 RC 2 available for testing

Comments

The sequence (?# marks the start of a comment which continues up to the next closing parenthesis. Nested parentheses are not permitted. The characters that make up a comment play no part in the pattern matching at all.

If the PCRE_EXTENDED option is set, an unescaped # character outside a character class introduces a comment that continues up to the next newline character in the pattern.

Example #1 Usage of comments in PCRE pattern

<?php

$subject 
'test';

/* (?# can be used to add comments without enabling PCRE_EXTENDED */
$match preg_match('/te(?# this is a comment)st/'$subject);
var_dump($match);

/* Whitespace and # is treated as part of the pattern unless PCRE_EXTENDED is enabled */
$match preg_match('/te   #~~~~
st/'
$subject);
var_dump($match);

/* When PCRE_EXTENDED is enabled, all whitespace data characters and anything
   that follows an unescaped # on the same line is ignored */
$match preg_match('/te    #~~~~
st/x'
$subject);
var_dump($match);

The above example will output:

int(1)
int(0)
int(1)

add a note add a note

User Contributed Notes 1 note

up
-2
asamaru at asamaru dot net
4 years ago
<?php
$string
= 'test';
echo
preg_match('/te(?# comments)st/', $string) . "\n";
echo
preg_match('/te#~~~~
st/'
, $string) . "\n";
echo
preg_match('/te#~~~~
st/x'
, $string) . "\n";

// result
// 1
// 0
// 1
To Top