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(PHP 4, PHP 5)
preg_split — Zerlegt eine Zeichenkette anhand eines regulären Ausdrucks
Zerlegt die angegebene Zeichenkette anhand eines regulären Ausdrucks.
Der Ausdruck, nach dem gesucht werden soll, als Zeichenkette.
Die zu zerlegende Zeichenkette.
Falls angegeben, werden maximal limit Teilzeichenketten zurückgegeben, wobei der Rest der Zeichenkette in der letzten Teilzeichenkette abgelegt wird. Ein limit von -1, 0 oder Null bedeutet "kein Limit" und wie es in PHP Standard ist, kann Null verwendet werden um den Parameter flags zu überspringen.
flags kann jede Kombination der folgenden Flags sein (verknüpft mit dem bitweisen | Operator):
Falls dieses Flag gesetzt ist, wird mit jeder gefundenen Übereinstimmung der dazugehörige Versatz in der Zeichenkette zurückgegeben. Beachten Sie, dass dies die Rückgabewerte in einem Array dahingehend ändert, dass jedes Element ein Array ist, das aus der übereinstimmenden Zeichenkette als Element 0 und deren Stelle in subject als Element 1 besteht.
Gibt ein Array zurück, bestehend aus Teilzeichenketten der Zeichenkette subject, die an den auf das Suchmuster pattern passenden Stellen zerlegt wurde.
| Version | Beschreibung |
|---|---|
| 4.3.0 | Das Flag PREG_SPLIT_OFFSET_CAPTURE hinzugefügt |
| 4.0.5 | Das Flag PREG_SPLIT_DELIM_CAPTURE hinzugefügt |
Beispiel #1 preg_split() Beispiel: Eine Zeichenkette in ihre Bestandteile zerlegen
<?php
// zerlegt die Zeichenkette an Stellen mit beliebiger Anzahl von
// Kommata oder Leerzeichen, die " ", \r, \t, \n und \f umfassen
$schluesselwoerter = preg_split("/[\s,]+/", "hypertext language, programming");
?>
Beispiel #2 Eine Zeichenkette in einzelne Zeichen zerlegen
<?php
$str = 'Zeichenkette';
$zeichen = preg_split('//', $str, -1, PREG_SPLIT_NO_EMPTY);
print_r($zeichen);
?>
Beispiel #3 Eine Zeichenkette in Übereinstimmungen mit dem Suchmuster und deren Versatz zerlegen
<?php
$str = 'hypertext language programming';
$zeichen = preg_split('/ /', $str, -1, PREG_SPLIT_OFFSET_CAPTURE);
print_r($zeichen);
?>
Das oben gezeigte Beispiel erzeugt folgende Ausgabe:
Array
(
[0] => Array
(
[0] => hypertext
[1] => 0
)
[1] => Array
(
[0] => language
[1] => 10
)
[2] => Array
(
[0] => programming
[1] => 19
)
)
Falls Sie die Leistung regulärer Ausdrücke nicht benötigen, können Sie stattdessen schnellere (wenngleich einfachere) Alternativen wie explode() oder str_split() verwenden.
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 \.
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
)
If you need to split a list of "tags" while allowing for user error, you'll find this more useful than the manual's first example.
<?php
$string = 'one, two,three, four , five,six seven';
$array = preg_split("/[\s]*[,][\s]*/", $string);
print_r($array);
// Array ( [0] => one [1] => two [2] => three [3] => four [4] => five [5] => six seven )
?>
This splits the string *only* by commas, regardless of how many spaces there are on either side of any comma.
Hope this helps someone...
<?php
/**
* Split a string into groups of words with a line no longer than $max
* characters.
*
* @param string $string
* @param integer $max
* @return array
**/
function split_words($string, $max = 1)
{
$words = preg_split('/\s/', $string);
$lines = array();
$line = '';
foreach ($words as $k => $word) {
$length = strlen($line . ' ' . $word);
if ($length <= $max) {
$line .= ' ' . $word;
} else if ($length > $max) {
if (!empty($line)) $lines[] = trim($line);
$line = $word;
} else {
$lines[] = trim($line) . ' ' . $word;
$line = '';
}
}
$lines[] = ($line = trim($line)) ? $line : $word;
return $lines;
}
?>
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] => .
)
To split a camel-cased string using preg_split() with lookaheads and lookbehinds:
<?php
function splitCamelCase($str) {
return preg_split('/(?<=\\w)(?=[A-Z])/', $str);
}
?>
If you want to use something like explode(PHP_EOL, $string) but for all combinations of \r and \n, try this one:
<?php
$text = "A\nB\rC\r\nD\r\rE\n\nF";
$texts = preg_split("/((\r(?!\n))|((?<!\r)\n)|(\r\n))/", $text);
?>
result:
array("A", "B", "C", "D", "", "E", "", "F");
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.
Spacing out your CamelCase using preg_replace:
<?php
function spacify($camel, $glue = ' ') {
return preg_replace( '/([a-z0-9])([A-Z])/', "$1$glue$2", $camel );
}
echo spacify('CamelCaseWords'), "\n"; // 'Camel Case Words'
echo spacify('camelCaseWords'), "\n"; // 'camel Case Words'
?>
Here's a helpful function to space out your CamelCase using preg_split:
<?php
function spacify($camel, $glue = ' ') {
return $camel[0] . substr(implode($glue, array_map('implode', array_chunk(preg_split('/([A-Z])/',
ucfirst($camel), -1, PREG_SPLIT_NO_EMPTY | PREG_SPLIT_DELIM_CAPTURE), 2))), 1);
}
echo spacify('CamelCaseWords'); // 'Camel Case Words'
echo spacify('camelCaseWords'); // 'camel Case Words'
?>
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"
how to display a shortened text string with an elipsis, but on word boundaries only.
<?php
function truncate($string, $max = 70, $rep = '...') {
$words = preg_split("/[\s]+/", $string);
$newstring = '';
$numwords = 0;
foreach ($words as $word) {
if ((strlen($newstring) + 1 + strlen($word)) < $max) {
$newstring .= ' '.$word;
++$numwords;
} else {
break;
}
}
if ($numwords < count($words)) {
$newstring .= $rep;
}
return $newstring;
}
?>
hope this helps someone! thanks for all the help from everyone else!!
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);
?>
<?php
$s = '<p>bleh blah</p><p style="one">one two three</p>';
$htmlbits = preg_split('/(<p( style="[-:a-z0-9 ]+")?>|<\/p>)/i', $s, -1, PREG_SPLIT_DELIM_CAPTURE);
print_r($htmlbits);
?>
Array
(
[0] =>
[1] => <p>
[2] => bleh blah
[3] => </p>
[4] =>
[5] => <p style="one">
[6] => style="one"
[7] => one two three
[8] => </p>
[9] =>
)
two interesting bits:
1. When using PREG_SPLIT_DELIM_CAPTURE, if you use more than one pair of parentheses, the result array can have members representing all pairs. See array indexes 5 and 6 to see two adjacent delimiter results in which the second is a subset match of the first.
2. If a parenthesised sub-expression is made optional by a following question mark (ex: '/abc (optional subregex)?/') some split delimiters may be captured in the result while others are not. See array indexes 1 and 2 to see an instance where the overall match succeeded and returned a delimiter while the optional sub-expression '( style="[-:a-z0-9 ]+")?' did not match, and did not return a delimiter. This means it's possible to have a result with an unpredictable number of delimiters in the result array.
This second aspect is true irrespective of the number of pairs of parentheses in the regex. This means: in a regular expression with a single optional parenthesised sub-expression, the overall expression can match without generating a corresponding delimiter in the result.
For people who want to use the double quote to group words/fields, kind of like CSV does, you can use the following expression:
<?php
$keywords = preg_split( "/[\s,]*\\\"([^\\\"]+)\\\"[\s,]*|[\s,]+/", "textline with, commas and \"quoted text\" inserted", 0, PREG_SPLIT_DELIM_CAPTURE );
?>
Which will result in:
Array
(
[0] => textline
[1] => with
[2] => commas
[3] => and
[4] => quoted text
[5] => inserted
)
I was having trouble getting the PREG_SPLIT_DELIM_CAPTURE flag to work because I missed reading the "parenthesized expression" in the documentation :-(
So the pattern should look like:
/(A)/
not just
/A/
and it works as described/expected.
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.
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
The above description for PREG_SPLIT_OFFSET_CAPTURE may be a bit confusing.
When the flag is or'd into the 'flags' parameter of preg_split, each match is returned in the form of a two-element array. For each of the two-element arrays, the first element is the matched string, while the second is the match's zero-based offset in the input string.
For example, if you called preg_split like this:
preg_split('/foo/', 'matchfoomatch', -1, PREG_SPLIT_OFFSET_CAPTURE);
it would return an array of the form:
Array(
[0] => Array([0] => "match", [1] => 0),
[1] => Array([1] => "match", [1] => 8)
)
Note that or'ing in PREG_DELIM_CAPTURE along with PREG_SPLIT_OFFSET_CAPTURE works as well.
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