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Match details

When using pattern()->match() and pattern()->replace->callback(), some methods receive a callback that accepts Detail details object. These methods are: first(), findFirst(), forEach(), map(), flatMap(), callback().

The details can be used to get concise information about the matched occurrence, such as its value (i.e. "the whole match"), capturing groups and their UTF-8/raw offsets, limits, indexes, other matches as well as the used subject (although it could also be pass as a closure parameter) and more.

For example, to read the offset at which the occurrence was matched, use Detail.offset():

pattern('[A-Z][a-z]+')->match('I like Trains')->first(fn(Detail $detail) => $detail->offset());


Using Detail details, you gain access to:

  • text() - value of a matched occurrence
  • toInt()/isInt() which allow you to handle integers safely
  • subject() - subject against which the pattern was matched
  • index() - ordinal value of a matched occurrence
  • limit() - limit which was put on the matches
  • offsets of matched values in the subject (UTF-8 safe):
  • byte versions of the methods:
    • byteTextLength()
    • byteOffset()
    • byteTail()
  • all() - other matched occurrences
  • details about capturing groups, in the next chapter: Capturing groups
  • User data - sharing custom data between callbacks

Matched text#

There are 6 similar ways to get the value of the matched occurrence.

pattern('[A-Z][a-z]+')->match('I like Trains')->map(function (Detail $detail) {
return $detail->text(); // using text() method
return $detail->group(0)->text(); // group #0 is the whole match in all regexp engines
return (string) $detail; // cast it to string
return (string) $detail->group(0); // cast group #0 to string
return "$detail"; // enclose it in double quotes

or you can just accept string in the callback signature.

pattern('[A-Z][a-z]+')->match('I like Trains')->map(function (string $match) {
return $match;

All of them are redundant and equal to each other. Their redundancy comes from the fact the there are a few ways of casting an object to string in PHP, casting Detail to string is the same as getting text() in T-Regx, and that the whole match is also group 0 in regular expressions.

There's also UTF8-safe method textLength() which, you guessed it, returns the length of a matched text.

pattern('[A-Z][a-z]+')->match('I like Trains')->map(function (Detail $detail) {
return $detail->text(); // 'Trains'
return $detail->textLength(); // 6


Method isInt() returns true if, and only if, the matched occurrence is numeric. And by "numeric", we mean "real" numeric, not PHP numeric:

  • String values considered valid integers:
    • '14', '-14', '000'
  • Strings that aren't treated as valid integers:
    • '+14', ' 10', '10 ', '', ' ', '0.0', '0,0',

The string is considered a valid integer if:

  • contains only 0-9 characters, and more than 1 of them (so 00 is also a valid integer, but '' isn't)
  • optionally starts with only one - sign
  • its numeric representation is:
    • higher than PHP_INT_MIN (-9223372036854775808)
    • lower than PHP_INT_MAX (9223372036854775807)
  • doesn't contain any other characters

Checking and parsing#

There are two methods regarding integers: isInt() and toInt().

$detail->isInt() returns true/false depending on whether the matched occurrence is numeric. toInt() returns said numeric occurrence as an integer, or throws IntegerFormatException instead.

pattern('\d+')->match('User input was: 4 times')->first(function (Detail $detail) {
if ($detail->isInt()) {
for ($i = 0; $i < $detail->toInt(); $i++) {
// tasks

It's implemented with filter_var(), but you can think of it as /^-?\d+$/ with max/min values check.


To get the subject in your callback, use Detail.subject():

pattern('[A-Z][a-z]+')->match('I like Trains')->map(fn(Detail $detail) => $detail->subject());
'I like Trains'

This is equivalent to storing the subject in a variable and using it in your closure.

$subject = 'I like Trains';
pattern('[A-Z][a-z]+')->match($subject)->map(fn(Detail $detail) => $subject);

Ordinal value (index)#

Detail.index() returns the ordinal number of a matched occurrence.

In this example, we'll modify every second word:

pattern('\w+')->match('I like Trains, but I also like bikes')->map(function (Detail $detail) {
if ($detail->index() % 2 === 0) {
return strtolower($detail);
return strtoupper($detail);
['i', 'LIKE', 'trains', 'BUT', 'i', 'ALSO', 'like', 'BIKES']


Depending on whether you used all(), first() or only(int) - method limit() will return -1, 1 or an argument given to only()

pattern('\w+')->replace($string)->all()->callback(function (Detail $detail) {
$detail->limit(); // -1
pattern('\w+')->replace($string)->first()->callback(function (Detail $detail) {
$detail->limit(); // 1
pattern('\w+')->replace($string)->only(5)->callback(function (Detail $detail) {
$detail->limit(); // 5


Detail.offset() can be used to get the offset of the matched occurrence in the subject. Detail.offset() is multi-byte character safe and returns offset in characters, whereas Detail.byteOffset() returns the offset in bytes.

pattern('here')->match('Apples for 0.30€, here')->first(function (Detail $detail) {
$characters = $detail->offset(); // 18
$byes = $detail->byteOffset(); // 20

Here's what the numbers mean:

Apples for 0.30€, here
A p p l e s f o r 0 . 3 0 € , h e r e
65 112 112 108 101 115 32 102 111 114 32 48 46 51 48 226 130 172 44 32 104 101 114 101

In other words, offset() treats bytes [226, 130, 172] as one multi-byte character (euro sign ) and counts them as one; whereas byteOffset() would count them as three.



Method Detail.tail() simply returns the position of the last character in a matched occurrence.

pattern('ipsum')->match('Lorem ipsum')->first(function (Detail $detail) {
$start = $detail->offset(); // 6
$end = $detail->tail(); // 11

There's also Detail.byteTail() which returns the tail in bytes, instead of characters.

Other occurrences#

Detail has access to other matched occurrences:

  • Detail.all() - for whole matches (like Detail.text())
  • - for capturing groups (like

Even if you use first() or only(int) methods, Detail.all() always returns unlimited occurrences.

pattern('\w+')->match('Apples are cool')->map(function (Detail $detail) {
return [
'match' => $detail->text(),
'all' => $detail->all()
['match' => 'Apples', 'all' => ['Apples', 'are', 'cool']],
['match' => 'are', 'all' => ['Apples', 'are', 'cool']],
['match' => 'cool', 'all' => ['Apples', 'are', 'cool']]


With|int), you can easily retrieve capturing groups.

Just like with Detail, retrieving matched occurrence value is done with text() method or by casting it to string.

$pattern = '(?<value>\d+)(?<unit>cm|mm)';
$subject = '192mm and 168cm or 18mm and 12cm';
pattern($pattern)->match($subject)->first(function (Detail $detail) {
$text = $detail->text(); // '192mm'
$value = (string) $detail->group('value'); // '192'
$unit = $detail->group('unit')->text(); // 'mm'

More about capturing groups can be found in the next section: Capturing groups.

User data#

To most users this functionality will occur as redundant - it's only use case are multiple calls to callbacks, for example when using chained filter()->map(). With user data, it's possible to perform an operation in filter(), store its value in user data, and then use the value in map() without reference closure variables.

pattern('\w{2}')->match('Languages: en, de, xd, sv')
->filter(function (Detail $detail) {
$languageInfo = HeavyService::fetch($detail->text());
return $languageInfo->isValid();
->map(function (Detail $detail) {
$languageInfo = $detail->getUserData();
return $languageInfo->languages():
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