String Functions

Nette\Utils\Strings is a static class containing useful functions for working with UTF-8 encoded strings.

Installation:

composer require nette/utils

All examples assume the following class alias is defined:

use Nette\Utils\Strings;

Letter Case

These functions require the PHP extension mbstring.

lower (string $s): string

Converts a UTF-8 string to lowercase.

Strings::lower('Hello World'); // 'hello world'

upper (string $s): string

Converts a UTF-8 string to uppercase.

Strings::upper('Hello World'); // 'HELLO WORLD'

firstUpper (string $s): string

Converts the first character of a UTF-8 string to uppercase and leaves the other characters unchanged.

Strings::firstUpper('hello world'); // 'Hello world'

firstLower (string $s): string

Converts the first character of a UTF-8 string to lowercase and leaves the other characters unchanged.

Strings::firstLower('Hello World'); // 'hello world'

capitalize (string $s): string

Converts the first character of every word in a UTF-8 string to uppercase and the others to lowercase.

Strings::capitalize('hello world'); // 'Hello World'

Editing a String

normalize (string $s): string

Removes control characters, normalizes line endings to \n, trims leading and trailing blank lines, trims trailing spaces on lines, and normalizes UTF-8 to the NFC normal form.

unixNewLines (string $s): string

Converts line endings to \n used on Unix systems. Line endings are: \n, \r, \r\n, U+2028 line separator, U+2029 paragraph separator.

$unixLikeLines = Strings::unixNewLines($string);

platformNewLines (string $s): string

Converts line endings to characters specific to the current platform, i.e., \r\n on Windows and \n elsewhere. Line endings are: \n, \r, \r\n, U+2028 line separator, U+2029 paragraph separator.

$platformLines = Strings::platformNewLines($string);

webalize (string $s, ?string $charlist=null, bool $lower=true): string

Modifies a UTF-8 string to the form used in URLs, i.e., removes diacritics and replaces all characters except letters of the English alphabet and numbers with hyphens.

Strings::webalize('žluťoučký kůň'); // 'zlutoucky-kun'

If other characters should be preserved, they can be specified in the second parameter.

Strings::webalize('10. image_id', '._'); // '10.-image_id'

The third parameter can suppress conversion to lowercase.

Strings::webalize('Dobrý den', null, false); // 'Dobry-den'

Requires the PHP extension intl.

trim (string $s, ?string $charlist=null): string

Strips leading and trailing whitespace (or other characters specified by the second parameter) from a UTF-8 string.

Strings::trim('  Hello  '); // 'Hello'

truncate (string $s, int $maxLen, string $append=`'…'`): string

Truncates a UTF-8 string to the specified maximum length, trying to preserve whole words. If the string is truncated, an ellipsis (changeable via the third parameter) is added to the end.

$text = 'Hello, how are you today?';
Strings::truncate($text, 5);       // 'Hell…'
Strings::truncate($text, 20);      // 'Hello, how are you…'
Strings::truncate($text, 30);      // 'Hello, how are you today?'
Strings::truncate($text, 20, '~'); // 'Hello, how are you~'

indent (string $s, int $level=1, string $indentationChar=`"\t"`): string

Indents a multiline text from the left. The second parameter specifies the number of indentation characters, and the third parameter specifies the character(s) to use for indentation (default is tab).

Strings::indent('Nette');         // "\tNette"
Strings::indent('Nette', 2, '+'); // '++Nette'

padLeft (string $s, int $length, string $pad=`' '`): string

Pads a UTF-8 string to a specified length by prepending the $pad string from the left.

Strings::padLeft('Nette', 6);        // ' Nette'
Strings::padLeft('Nette', 8, '+*');  // '+*+Nette'

padRight (string $s, int $length, string $pad=`' '`): string

Pads a UTF-8 string to a specified length by appending the $pad string from the right.

Strings::padRight('Nette', 6);       // 'Nette '
Strings::padRight('Nette', 8, '+*'); // 'Nette+*+'

substring (string $s, int $start, ?int $length=null): string

Returns a portion of a UTF-8 string $s specified by the starting position $start and length $length. If $start is negative, the returned string will start at the $start-th character from the end.

Strings::substring('Nette Framework', 0, 5); // 'Nette'
Strings::substring('Nette Framework', 6);    // 'Framework'
Strings::substring('Nette Framework', -4);   // 'work'

reverse (string $s): string

Reverses a UTF-8 string.

Strings::reverse('Nette'); // 'etteN'

length (string $s): int

Returns the number of characters (not bytes) in a UTF-8 string.

This is the number of Unicode code points, which may differ from the number of graphemes.

Strings::length('Nette');   // 5
Strings::length('červená'); // 7

startsWith (string $haystack, string $needle): bool

Checks if the string $haystack starts with the string $needle.

$haystack = 'Starts';
$needle = 'St';
Strings::startsWith($haystack, $needle); // true

Use the native str_starts_with() function.

endsWith (string $haystack, string $needle): bool

Checks if the string $haystack ends with the string $needle.

$haystack = 'Ends';
$needle = 'ds';
Strings::endsWith($haystack, $needle); // true

Use the native str_ends_with() function.

contains (string $haystack, string $needle): bool

Checks if the string $haystack contains the string $needle.

$haystack = 'Auditorium';
$needle = 'dit';
Strings::contains($haystack, $needle); // true

Use the native str_contains() function.

compare (string $left, string $right, ?int $length=null): bool

Compares two UTF-8 strings or their parts, case-insensitively. If $length is null, compares the entire strings. If negative, compares the corresponding number of characters from the end of the strings. Otherwise, compares the corresponding number of characters from the beginning.

Strings::compare('Nette', 'nette');     // true
Strings::compare('Nette', 'next', 2);   // true - first 2 characters match
Strings::compare('Nette', 'Latte', -2); // true - last 2 characters match

findPrefix (…$strings): string

Finds the common prefix of the strings. Returns an empty string if no common prefix is found.

Strings::findPrefix('prefix-a', 'prefix-bb', 'prefix-c');   // 'prefix-'
Strings::findPrefix(['prefix-a', 'prefix-bb', 'prefix-c']); // 'prefix-'
Strings::findPrefix('Nette', 'is', 'great');                // ''

before (string $haystack, string $needle, int $nth=1): ?string

Returns the portion of string $haystack before the $nth occurrence of string $needle. Returns null if $needle is not found. If $nth is negative, it searches from the end of the string.

Strings::before('Nette_is_great', '_', 1);  // 'Nette'
Strings::before('Nette_is_great', '_', -2); // 'Nette'
Strings::before('Nette_is_great', ' ');     // null
Strings::before('Nette_is_great', '_', 3);  // null

after (string $haystack, string $needle, int $nth=1): ?string

Returns the portion of string $haystack after the $nth occurrence of string $needle. Returns null if $needle is not found. If $nth is negative, it searches from the end of the string.

Strings::after('Nette_is_great', '_', 2);  // 'great'
Strings::after('Nette_is_great', '_', -1); // 'great'
Strings::after('Nette_is_great', ' ');     // null
Strings::after('Nette_is_great', '_', 3);  // null

indexOf (string $haystack, string $needle, int $nth=1): ?int

Returns the character position of the $nth occurrence of string $needle in string $haystack. Returns null if $needle is not found. If $nth is negative, it searches from the end of the string.

Strings::indexOf('abc abc abc', 'abc', 2);  // 4
Strings::indexOf('abc abc abc', 'abc', -1); // 8
Strings::indexOf('abc abc abc', 'd');       // null

Encoding

fixEncoding (string $s): string

Removes invalid UTF-8 characters from a string.

$correctString = Strings::fixEncoding($invalidString);

checkEncoding (string $s): bool

Checks if a string is a valid UTF-8 string.

$isUtf8 = Strings::checkEncoding($string);

Use Nette\Utils\Validator::isUnicode().

toAscii (string $s): string

Converts a UTF-8 string to ASCII, i.e., removes diacritics, etc.

Strings::toAscii('žluťoučký kůň'); // 'zlutoucky kun'

Requires the PHP extension intl.

chr (int $code): string

Returns a specific character in UTF-8 from a code point (a number in the range 0×0000..D7FF or 0xE000..10FFFF).

Strings::chr(0xA9); // '©' in UTF-8 encoding

ord (string $char): int

Returns the code point of a specific character in UTF-8 (a number in the range 0×0000..D7FF or 0xE000..10FFFF).

Strings::ord('©'); // 169 (0xA9)

Regular Expressions

The Strings class offers functions for working with regular expressions. Unlike native PHP functions, they feature a more understandable API, better Unicode support, and, crucially, error detection. Any error during compilation or expression processing throws a Nette\RegexpException.

split (string $subject, string $pattern, bool $captureOffset=false, bool $skipEmpty=false, int $limit=-1, bool $utf8=false): array

Splits a string into an array using a regular expression. Expressions in parentheses will also be captured and returned.

Strings::split('hello, world', '~,\s*~');
// ['hello', 'world']

Strings::split('hello, world', '~(,)\s*~');
// ['hello', ',', 'world']

If $skipEmpty is true, only non-empty items will be returned:

Strings::split('hello, world, ', '~,\s*~');
// ['hello', 'world', '']

Strings::split('hello, world, ', '~,\s*~', skipEmpty: true);
// ['hello', 'world']

If $limit is specified, only substrings up to the limit are returned, and the rest of the string is placed in the last element. A limit of –1 or 0 means no limit.

Strings::split('hello, world, third', '~,\s*~', limit: 2);
// ['hello', 'world, third']

If $utf8 is true, evaluation switches to Unicode mode, similar to using the u modifier.

If $captureOffset is true, the position of each match in the string will also be returned (in bytes; in characters if $utf8 is set). This changes the return value to an array where each element is a pair consisting of the matched string and its position.

Strings::split('žlutý, kůň', '~,\s*~', captureOffset: true);
// [['žlutý', 0], ['kůň', 9]]

Strings::split('žlutý, kůň', '~,\s*~', captureOffset: true, utf8: true);
// [['žlutý', 0], ['kůň', 7]] // positions are in characters

match (string $subject, string $pattern, bool $captureOffset=false, int $offset=0, bool $unmatchedAsNull=false, bool $utf8=false): ?array

Searches a string for a part matching a regular expression and returns an array containing the found expression and individual subexpressions, or null if no match is found.

Strings::match('hello!', '~\w+(!+)~');
// ['hello!', '!']

Strings::match('hello!', '~X~');
// null

If $unmatchedAsNull is true, unmatched subpatterns are returned as null; otherwise, they are returned as an empty string or omitted entirely:

Strings::match('hello', '~\w+(!+)?~');
// ['hello'] (the optional group !+ did not match)

Strings::match('hello', '~\w+(!+)?~', unmatchedAsNull: true);
// ['hello', null]

If $utf8 is true, evaluation switches to Unicode mode, similar to using the u modifier:

Strings::match('žlutý kůň', '~\w+~'); // Without UTF-8
// ['lut'] (matches only ASCII word characters)

Strings::match('žlutý kůň', '~\w+~', utf8: true); // With UTF-8
// ['žlutý'] (matches Unicode word characters)

The $offset parameter can specify the starting position for the search (in bytes; in characters if $utf8 is set).

Strings::match('žlutý!', '~\w+(!+)?~', captureOffset: true); // Without UTF-8
// [['lut', 2]] (only ASCII match, offset in bytes)

Strings::match('žlutý!', '~\w+(!+)?~', captureOffset: true, utf8: true); // With UTF-8
// [['žlutý!', 0], ['!', 5]] (Unicode match, offsets in characters)

matchAll (string $subject, string $pattern, bool $captureOffset=false, int $offset=0, bool $unmatchedAsNull=false, bool $patternOrder=false, bool $utf8=false, bool $lazy=false): array|Generator

Searches a string for all occurrences matching a regular expression and returns an array of arrays containing the found expression and individual subexpressions.

Strings::matchAll('hello, world!!', '~\w+(!+)?~');
/* [
	0 => ['hello'],
	1 => ['world!!', '!!'],
] */

If $patternOrder is true, the structure of the results changes: the first element is an array of full pattern matches, the second is an array of strings matching the first parenthesized subpattern, and so on:

Strings::matchAll('hello, world!!', '~\w+(!+)?~', patternOrder: true);
/* [
	0 => ['hello', 'world!!'],
	1 => ['', '!!'],
] */

If $unmatchedAsNull is true, unmatched subpatterns are returned as null; otherwise, they are returned as an empty string or omitted:

Strings::matchAll('hello, world!!', '~\w+(!+)?~', unmatchedAsNull: true);
/* [
	0 => ['hello', null],
	1 => ['world!!', '!!'],
] */

If $utf8 is true, evaluation switches to Unicode mode, similar to using the u modifier:

Strings::matchAll('žlutý kůň', '~\w+~');
/* [
	0 => ['lut'],
	1 => ['k'],
] */

Strings::matchAll('žlutý kůň', '~\w+~', utf8: true);
/* [
	0 => ['žlutý'],
	1 => ['kůň'],
] */

The $offset parameter can specify the starting position for the search (in bytes; in characters if $utf8 is set).

If $captureOffset is true, the position of each match in the string will also be returned (in bytes; in characters if $utf8 is set). This changes the return value structure, where each match element is a pair matched_string, position:

Strings::matchAll('žlutý kůň', '~\w+~', captureOffset: true);
/* [
	0 => [['lut', 2]],
	1 => [['k', 8]],
] */

Strings::matchAll('žlutý kůň', '~\w+~', captureOffset: true, utf8: true);
/* [
	0 => [['žlutý', 0]],
	1 => [['kůň', 6]],
] */

If $lazy is true, the function returns a Generator instead of an array. This offers significant performance benefits when working with large strings, as matches are found incrementally rather than processing the entire string at once. This allows efficient handling of extremely large inputs. Additionally, you can interrupt processing at any time if you find the desired match, saving computation time.

$matches = Strings::matchAll($largeText, '~\w+~', lazy: true);
foreach ($matches as $match) {
    echo "Found: $match[0]\n";
    // Processing can be interrupted at any time, e.g., with break;
}

replace (string $subject, string|array $pattern, string|callable $replacement=`''`, int $limit=-1, bool $captureOffset=false, bool $unmatchedAsNull=false, bool $utf8=false): string

Replaces all occurrences matching a regular expression. $replacement is either a replacement string mask or a callback function.

Strings::replace('hello, world!', '~\w+~', '--');
// '--, --!'

Strings::replace('hello, world!', '~\w+~', fn($m) => strrev($m[0]));
// 'olleh, dlrow!'

The function also allows multiple replacements by passing an array in the format pattern => replacement as the second parameter:

Strings::replace('hello, world!', [
	'~\w+~' => '--',
	'~,\s+~' => ' ',
]);
// '-- --!'

The $limit parameter restricts the number of replacements performed. A limit of –1 means no limit.

If $utf8 is true, evaluation switches to Unicode mode, similar to using the u modifier.

Strings::replace('žlutý kůň', '~\w+~', '--');
// 'ž--ý --ůň'

Strings::replace('žlutý kůň', '~\w+~', '--', utf8: true);
// '-- --'

If $captureOffset is true, the position of each match in the string (in bytes; in characters if $utf8 is set) is also passed to the callback. This changes the structure of the passed array, where each element is a pair matched_string, position.

Strings::replace(
	'žlutý kůň',
	'~\w+~',
	function (array $m) { dump($m); return ''; },
	captureOffset: true,
);
// dumps [['lut', 2]] and [['k', 8]]

Strings::replace(
	'žlutý kůň',
	'~\w+~',
	function (array $m) { dump($m); return ''; },
	captureOffset: true,
	utf8: true,
);
// dumps [['žlutý', 0]] and [['kůň', 6]]

If $unmatchedAsNull is true, unmatched subpatterns are passed to the callback as null; otherwise, they are passed as an empty string or omitted:

Strings::replace(
	'ac',
	'~(a)(b)*(c)~',
	function (array $m) { dump($m); return ''; },
);
// dumps ['ac', 'a', '', 'c']

Strings::replace(
	'ac',
	'~(a)(b)*(c)~',
	function (array $m) { dump($m); return ''; },
	unmatchedAsNull: true,
);
// dumps ['ac', 'a', null, 'c']

String Functions

Letter Case

lower (string $s): string

upper (string $s): string

firstUpper (string $s): string

firstLower (string $s): string

capitalize (string $s): string

Editing a String

normalize (string $s): string

unixNewLines (string $s): string

platformNewLines (string $s): string

webalize (string $s, ?string $charlist=null, bool $lower=true): string

trim (string $s, ?string $charlist=null): string

truncate (string $s, int $maxLen, string $append=`'…'`): string

indent (string $s, int $level=1, string $indentationChar=`"\t"`): string

padLeft (string $s, int $length, string $pad=`' '`): string

padRight (string $s, int $length, string $pad=`' '`): string

substring (string $s, int $start, ?int $length=null): string

reverse (string $s): string

length (string $s): int

startsWith (string $haystack, string $needle): bool

endsWith (string $haystack, string $needle): bool

contains (string $haystack, string $needle): bool

compare (string $left, string $right, ?int $length=null): bool

findPrefix (…$strings): string

before (string $haystack, string $needle, int $nth=1): ?string

after (string $haystack, string $needle, int $nth=1): ?string

indexOf (string $haystack, string $needle, int $nth=1): ?int

Encoding

fixEncoding (string $s): string

checkEncoding (string $s): bool

toAscii (string $s): string

chr (int $code): string

ord (string $char): int

Regular Expressions

split (string $subject, string $pattern, bool $captureOffset=false, bool $skipEmpty=false, int $limit=-1, bool $utf8=false): array

match (string $subject, string $pattern, bool $captureOffset=false, int $offset=0, bool $unmatchedAsNull=false, bool $utf8=false): ?array

matchAll (string $subject, string $pattern, bool $captureOffset=false, int $offset=0, bool $unmatchedAsNull=false, bool $patternOrder=false, bool $utf8=false, bool $lazy=false): array|Generator

replace (string $subject, string|array $pattern, string|callable $replacement='', int $limit=-1, bool $captureOffset=false, bool $unmatchedAsNull=false, bool $utf8=false): string

replace (string $subject, string|array $pattern, string|callable $replacement=`''`, int $limit=-1, bool $captureOffset=false, bool $unmatchedAsNull=false, bool $utf8=false): string