preg_split

(PHP 4, PHP 5, PHP 7, PHP 8)

preg_split — Divide un string mediante una expresión regular

Descripción

preg_split(
    string $pattern,
    string $subject,
    int $limit = -1,
    int $flags = 0
): array

Divide el string dado mediante una expresión regular.

Parámetros

pattern

El patrón de búsqueda, dado como string.

subject

El string de entrada.

limit

Si se especifica, son devueltos únicamente los substrings hasta limit, con el resto del string colocado en el último substring. Si limit vale -1 o 0 significa "sin límite".

flags

flags puede ser una combinación de las siguientes banderas (combinadas con el operador | de bits):

PREG_SPLIT_NO_EMPTY: Si se aplica esta bandera, solo serán devueltos los elementos no vacíos por preg_split().
PREG_SPLIT_DELIM_CAPTURE: Si se aplica esta bandera, las expresiones entre paréntesis en el patrón delimitador serán capturadas y devueltas.
PREG_SPLIT_OFFSET_CAPTURE: Si se aplica esta bandera, por cada coincidencia producida, el índice del string añadido también será devuelto. Observe que esto cambia el valor devuelto dentro de un array donde cada elemento es un array consistente en el string coincidente en el índice 0 y su índice de string dentro de subject en el índice 1.

Valores devueltos

Devuelve un array que contiene substrings de subject dividido por los límites coincidentes de pattern, o false en caso de error.

Errores/Excepciones

If the regex pattern passed does not compile to a valid regex, an E_WARNING is emitted.

Ejemplos

Ejemplo #1 Ejemplo de preg_split() : Obtener las partes de un string de búsqueda

<?php
// divide la frase mediante cualquier número de comas o caracteres de espacio,
// lo que incluye " ", \r, \t, \n y \f
$claves = preg_split("/[\s,]+/", "hypertext language, programming");
print_r($claves);
?>

El resultado del ejemplo sería:

Array
(
    [0] => hypertext
    [1] => language
    [2] => programming
)

Ejemplo #2 Dividir un string en sus caracteres constituyentes

<?php
$str = 'string';
$caracteres = preg_split('//', $str, -1, PREG_SPLIT_NO_EMPTY);
print_r($caracteres);
?>

El resultado del ejemplo sería:

Array
(
    [0] => s
    [1] => t
    [2] => r
    [3] => i
    [4] => n
    [5] => g
)

Ejemplo #3 Dividir un string mediante coincidencias y sus índices

<?php
$str = 'hypertext language programming';
$caracteres = preg_split('/ /', $str, -1, PREG_SPLIT_OFFSET_CAPTURE);
print_r($caracteres);
?>

El resultado del ejemplo sería:

Array
(
    [0] => Array
        (
            [0] => hypertext
            [1] => 0
        )

    [1] => Array
        (
            [0] => language
            [1] => 10
        )

    [2] => Array
        (
            [0] => programming
            [1] => 19
        )

)

Notas

Sugerencia

Si no necesita la potencia de expresiones regulares, puede optar por alternativas más rápidas (no obstante más sencillas) como explode() o str_split().

Sugerencia

Si la comparación falla, será devuelto un array con un único elemento que contiene el string de entrada.

Ver también

Patrones de PCRE
preg_quote() - Escapar caracteres en una expresión regular
implode() - Une elementos de un array en un string
preg_match() - Realiza una comparación con una expresión regular
preg_match_all() - Realiza una comparación global de una expresión regular
preg_replace() - Realiza una búsqueda y sustitución de una expresión regular
preg_last_error() - Devuelve el código de error de la última ejecución de expresión regular de PCRE

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User Contributed Notes 18 notes

down

jan dot sochor at icebolt dot info ¶

15 years ago

Sometimes PREG_SPLIT_DELIM_CAPTURE does strange results.

<?php
$content = '<strong>Lorem ipsum dolor</strong> sit <img src="test.png" />amet <span class="test" style="color:red">consec<i>tet</i>uer</span>.';
$chars = preg_split('/<[^>]*[^\/]>/i', $content, -1, PREG_SPLIT_NO_EMPTY | PREG_SPLIT_DELIM_CAPTURE);
print_r($chars);
?>
Produces:
Array
(
    [0] => Lorem ipsum dolor
    [1] =>  sit <img src="test.png" />amet 
    [2] => consec
    [3] => tet
    [4] => uer
)

So that the delimiter patterns are missing. If you wanna get these patters remember to use parentheses.

<?php
$chars = preg_split('/(<[^>]*[^\/]>)/i', $content, -1, PREG_SPLIT_NO_EMPTY | PREG_SPLIT_DELIM_CAPTURE);
print_r($chars); //parentheses added
?>
Produces:
Array
(
    [0] => <strong>
    [1] => Lorem ipsum dolor
    [2] => </strong>
    [3] =>  sit <img src="test.png" />amet 
    [4] => <span class="test" style="color:red">
    [5] => consec
    [6] => <i>
    [7] => tet
    [8] => </i>
    [9] => uer
    [10] => </span>
    [11] => .
)

down

buzoganylaszlo at yahoo dot com ¶

15 years ago

Extending m.timmermans's solution, you can use the following code as a search expression parser:

<?php
$search_expression = "apple bear \"Tom Cruise\" or 'Mickey Mouse' another word";
$words = preg_split("/[\s,]*\\\"([^\\\"]+)\\\"[\s,]*|" . "[\s,]*'([^']+)'[\s,]*|" . "[\s,]+/", $search_expression, 0, PREG_SPLIT_NO_EMPTY | PREG_SPLIT_DELIM_CAPTURE);
print_r($words);
?>

The result will be:
Array
(
    [0] => apple
    [1] => bear
    [2] => Tom Cruise
    [3] => or
    [4] => Mickey Mouse
    [5] => another
    [6] => word
)

1. Accepted delimiters: white spaces (space, tab, new line etc.) and commas.

2. You can use either simple (') or double (") quotes for expressions which contains more than one word.

down

canadian dot in dot exile at gmail dot com ¶

8 years ago

This regular expression will split a long string of words into an array of sub-strings, of some maximum length, but only on word-boundries.

I use the reg-ex with preg_match_all(); but, I'm posting this example here (on the page for preg_split()) because that's where I looked when I wanted to find a way to do this.

Hope it saves someone some time.

<?php
// example of a long string of words
$long_string = 'Your IP Address will be logged with the submitted note and made public on the PHP manual user notes mailing list. The IP address is logged as part of the notes moderation process, and won\'t be shown within the PHP manual itself.';

// "word-wrap" at, for example, 60 characters or less
$max_len = 60;

// this regular expression will split $long_string on any sub-string of
// 1-or-more non-word characters (spaces or punctuation)
if(preg_match_all("/.{1,{$max_len}}(?=\W+)/", $long_string, $lines) !== False) {

    // $lines now contains an array of sub-strings, each will be approx.
    // $max_len characters - depending on where the last word ended and
    // the number of 'non-word' characters found after the last word
    for ($i=0; $i < count($lines[0]); $i++) {
        echo "[$i] {$lines[0][$i]}\n";
    }
}
?>

down

Hayley Watson ¶

5 years ago

Assuming you're using UTF-8, this function can be used to separate Unicode text into individual codepoints without the need for the multibyte extension.

<?php

preg_split('//u', $text, -1, PREG_SPLIT_NO_EMPTY);

?>

The words "English", "Español", and "Русский" are all seven letters long. But strlen would report string lengths 7, 8 and 14, respectively. The preg_split above would return a seven-element array in all three cases. 

It splits '한국어' into the array ['한', '국', '어'] instead of the 9-character array that str_split($text) would produce.

down

eric at clarinova dot com ¶

13 years ago

Here is another way to split a CamelCase string, which is a simpler expression than the one using lookaheads and lookbehinds: 

preg_split('/([[:upper:]][[:lower:]]+)/', $last, null, PREG_SPLIT_DELIM_CAPTURE|PREG_SPLIT_NO_EMPTY)

It makes the entire CamelCased word the delimiter, then returns the delimiters (PREG_SPLIT_DELIM_CAPTURE) and omits the empty values between the delimiters (PREG_SPLIT_NO_EMPTY)

down

Daniel Schroeder ¶

14 years ago

If you want to split by a char, but want to ignore that char in case it is escaped, use a lookbehind assertion.



In this example a string will be split by ":" but "\:" will be ignored:



<?php

$string='a:b:c\:d';

$array=preg_split('#(?<!\\\)\:#',$string);

print_r($array);

?>



Results into:



Array

(

    [0] => a

    [1] => b

    [2] => c\:d

)

down

dewi at dewimorgan dot com ¶

3 years ago

Beware that it is not safe to assume there are no empty values returned by PREG_SPLIT_NO_EMPTY, nor that you will see no delimiters if you use PREG_SPLIT_DELIM_CAPTURE, as there are some edge cases where these are not true.

<?php
# As expected, splitting a string by itself returns two empty strings:
var_export(preg_split("/x/", "x"));

array (
  0 => '',
  1 => '',
)

# But if we add PREG_SPLIT_NO_EMPTY, then instead of an empty array, we get the delimiter.
var_export(preg_split("/x/", "x", PREG_SPLIT_NO_EMPTY));

array (
  0 => 'x',
)

And if we try to split an empty string, then instead of an empty array, we get an empty string even with PREG_SPLIT_NO_EMPTY.
var_export(preg_split("/x/", "", PREG_SPLIT_NO_EMPTY));

array (
  0 => '',
)
?>

down

PhoneixSegovia at gmail dot com ¶

13 years ago

You must be caution when using lookbehind to a variable match.
For example:
'/(?<!\\\)\r?\n)/'
 to match a new line when not \ is before it don't go as spected as it match \r as the lookbehind (becouse isn't a \) and is optional before \n.

You must use this for example:
'/((?<!\\\|\r)\n)|((?<!\\\)\r\n)/'
That match a alone \n (not preceded by \r or \) or a \r\n not preceded by a \.

down

Steve ¶

19 years ago

preg_split() behaves differently from perl's split() if the string ends with a delimiter. This perl snippet will print 5:



my @a = split(/ /, "a b c d e ");

print scalar @a;



The corresponding php code prints 6:



<?php print count(preg_split("/ /", "a b c d e ")); ?>



This is not necessarily a bug (nowhere does the documentation say that preg_split() behaves the same as perl's split()) but it might surprise perl programmers.

down

php at dmi dot me dot uk ¶

15 years ago

To split a camel-cased string using preg_split() with lookaheads and lookbehinds:

<?php
function splitCamelCase($str) {
  return preg_split('/(?<=\\w)(?=[A-Z])/', $str);
}
?>

down

jetsoft at iinet.net.au ¶

20 years ago

To clarify the "limit" parameter and the PREG_SPLIT_DELIM_CAPTURE option,



<?php

$preg_split('(/ /)', '1 2 3 4 5 6 7 8', 4 ,PREG_SPLIT_DELIM_CAPTURE );

?>



returns:



('1', ' ', '2', ' ' , '3', ' ', '4 5 6 7 8')



So you actually get 7 array items not 4

down

csaba at alum dot mit dot edu ¶

15 years ago

If the task is too complicated for preg_split, preg_match_all might come in handy, since preg_split is essentially a special case.

I wanted to split a string on a certain character (asterisk), but only if it wasn't escaped (by a preceding backslash).  Thus, I should ensure an even number of backslashes before any asterisk meant as a splitter.  Look-behind in a regular expression wouldn't work since the length of the preceding backslash sequence can't be fixed.  So I turned to preg_match_all:

<?php
// split a string at unescaped asterisks
// where backslash is the escape character
$splitter = "/\\*((?:[^\\\\*]|\\\\.)*)/";
preg_match_all($splitter, "*$string", $aPieces, PREG_PATTERN_ORDER);
$aPieces = $aPieces[1];

// $aPieces now contains the exploded string
// and unescaping can be safely done on each piece
foreach ($aPieces as $idx=>$piece)
  $aPieces[$idx] = preg_replace("/\\\\(.)/s", "$1", $piece);
?>

down

david dot binovec at gmail dot com ¶

13 years ago

Limit = 1 may be confusing. The important thing is that in case of limit equals to 1 will produce only ONE substring. Ergo the only one substring will be the first one as well as the last one. Tnat the rest of the string (after the first delimiter) will be placed to the last substring. But last is the first and only one.

<?php

$output = $preg_split('(/ /)', '1 2 3 4 5 6 7 8', 1); 

echo $output[0] //will return whole string!;

$output = $preg_split('(/ /)', '1 2 3 4 5 6 7 8', 2); 

echo $output[0] //will return 1;
echo $output[1] //will return '2 3 4 5 6 7 8';

?>

down

Miller ¶

10 years ago

This is a function to truncate a string of text while preserving the whitespace (for instance, getting an excerpt from an article while maintaining newlines). It will not jive well with HTML, of course.

<?php
/**
 * Truncates a string of text by word count
 * @param string $text The text to truncate
 * @param int $max_words The maximum number of words
 * @return string The truncated text
 */
function limit_words ($text, $max_words) {
    $split = preg_split('/(\s+)/', $text, -1, PREG_SPLIT_DELIM_CAPTURE);
    $truncated = '';
    for ($i = 0; $i < min(count($split), $max_words*2); $i += 2) {
        $truncated .= $split[$i].$split[$i+1];
    }
    return trim($truncated);
}
?>

down

Walf ¶

2 years ago

Using PREG_SPLIT_DELIM_CAPTURE without PREG_SPLIT_NO_EMPTY guarantees that all the odd-numbered keys in the result will contain the delimiters. This makes further processing more predictable, and empty strings can always be filtered out at the end.

down

kenorb at gmail dot com ¶

15 years ago

If you need convert function arguments without default default values and references, you can try this code:

<?php
    $func_args = '$node, $op, $a3 = NULL, $form = array(), $a4 = NULL'
    $call_arg = preg_match_all('@(?<func_arg>\$[^,= ]+)@i', $func_args, $matches);
    $call_arg = implode(',', $matches['func_arg']);
?>
Result: string = "$node,$op,$a3,$form,$a4"

down

-3

markac ¶

9 years ago

Split string into words.

<?php
$string = 'This - is a, very dirty "string" :-)';

// split into words
$wordlist = preg_split('/\W/', $string, 0, PREG_SPLIT_NO_EMPTY);

// returns only words that have minimum 2 chars
$wordlist = array_filter($wordlist, function($val) {
  return strlen($val) >= 2;
});

// print
var_dump($wordlist);
?>

Result:

array (size=5)
  0 => string 'This' (length=4)
  1 => string 'is' (length=2)
  3 => string 'very' (length=4)
  4 => string 'dirty' (length=5)
  5 => string 'string' (length=6)

down

-3

php at haravikk dot me ¶

7 years ago

When using the PREG_SPLIT_OFFSET_CAPTURE option you will end up with all results in a single array, which is often undesirable as it means you then have to filter out any delimiters you wanted to check for but not keep.

To get around this you can instead use preg_match_all() to perform the split. For comparison, here are two examples, both splitting around colon and semi-colon characters:

<?php $pieces_with_delimiters = preg_split('/[;:]/', $input, -1, PREG_SPLIT_OFFSET_CAPTURE); ?>

<?php preg_match_all('/([^;:]*)([;:]|$)/', $input, $matches);
list(, $pieces, $delimiters) = $matches ?>

The latter requires a more complex pattern, but produces a much more convenient set of results to work with, depending upon what you want to do with them.

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