Compzone.Org :: Podręcznik PHP :: preg_replace

Podręcznik PHP
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preg_replace

(PHP 3 >= 3.0.9, PHP 4, PHP 5)

preg_replace -- Perform a regular expression search and replace

Opis

mixed preg_replace ( mixed pattern, mixed replacement, mixed subject [, int limit [, int &count]] )

Searches subject for matches to pattern and replaces them with replacement.

Replacement may contain references of the form \\n or (since PHP 4.0.4) $n, with the latter form being the preferred one. Every such reference will be replaced by the text captured by the n'th parenthesized pattern. n can be from 0 to 99, and \\0 or $0 refers to the text matched by the whole pattern. Opening parentheses are counted from left to right (starting from 1) to obtain the number of the capturing subpattern.

When working with a replacement pattern where a backreference is immediately followed by another number (i.e.: placing a literal number immediately after a matched pattern), you cannot use the familiar \\1 notation for your backreference. \\11, for example, would confuse preg_replace() since it does not know whether you want the \\1 backreference followed by a literal 1, or the \\11 backreference followed by nothing. In this case the solution is to use \${1}1. This creates an isolated $1 backreference, leaving the 1 as a literal.

If subject is an array, then the search and replace is performed on every entry of subject, and the return value is an array as well.

The e modifier makes preg_replace() treat the replacement parameter as PHP code after the appropriate references substitution is done. Tip: make sure that replacement constitutes a valid PHP code string, otherwise PHP will complain about a parse error at the line containing preg_replace().

Parametry

pattern: The pattern to search for. It can be either a string or an array with strings.
replacement: The string or an array with strings to replace. If this parameter is a string and the pattern parameter is an array, all pattens will be replaced by that string. If both pattern and replacement parameters are arrays, each pattern will be replaced by the replacement counterpart. If there are less keys in the replacement array than in the pattern array, the excedent patterns will be replaced by an empty string.
subject: The string or an array with strings to search and replace.
limit: The maximum possible replacements for each pattern in each subject string. Defaults to -1 (no limit).
count: If specified, this variable will be filled with the number of replacements done.

Zwracane wartości

preg_replace() returns an array if the subject parameter is an array, or a string otherwise.

If matches are found, the new subject will be returned, otherwise subject will be returned unchanged.

Rejestr zmian

Wersja	Opis
4.0.1pl2	Added the `limit` parameter
4.0.4	Added the '$n' form for the `replacement` parameter
5.1.0	Added the `count` parameter

Przykłady

Przykład 1. Using backreferences followed by numeric literals

<?php

                $string = 'April 15, 2003';

                $pattern = '/(\w+) (\d+), (\d+)/i';

                $replacement = '${1}1,$3';

                echo preg_replace($pattern, $replacement, $string);
?>

Powyższy przykład wyświetli:

April1,2003

Przykład 2. Using indexed arrays with preg_replace()

<?php

                $string = 'The quick brown fox jumped over the lazy dog.';

                $patterns[0] = '/quick/';
$patterns[1] = '/brown/';
$patterns[2] = '/fox/';
$replacements[2] = 'bear';
$replacements[1] = 'black';
$replacements[0] = 'slow';

                echo preg_replace($patterns, $replacements, $string);
?>

Powyższy przykład wyświetli:

The bear black slow jumped over the lazy dog.

By ksorting patterns and replacements, we should get what we wanted.

<?php

                ksort($patterns);
ksort($replacements);

                echo preg_replace($patterns, $replacements, $string);
?>

Powyższy przykład wyświetli:

The slow black bear jumped over the lazy dog.

Przykład 3. Replacing several values

<?php

                $patterns = array ('/(19|20)(\d{2})-(\d{1,2})-(\d{1,2})/',


                                   '/^\s*{(\w+)}\s*=/');

                $replace = array ('\3/\4/\1\2', '$\1 =');

                echo preg_replace($patterns, $replace, '{startDate} = 1999-5-27');

                ?>

Powyższy przykład wyświetli:

$startDate = 5/27/1999

Przykład 4. Using the 'e' modifier

<?php

                preg_replace("/(<\/?)(\w+)([^>]*>)/e", 


                             "'\\1'.strtoupper('\\2').'\\3'", 


                             $html_body);
?>

This would capitalize all HTML tags in the input text.

Przykład 5. Strip whitespace

This example strips excess whitespace from a string.

<?php

                $str = 'foo   o';
$str = preg_replace('/\s\s+/', ' ', $str);
// This will be 'foo o' now
echo $str;

                ?>

Przykład 6. Using the count parameter

<?php

                $count = 0;

                

                echo preg_replace(array('/\d/', '/\s/'), '*', 'xp 4 to', -1 , $count);

                echo $count; //3
?>

Powyższy przykład wyświetli:

xp***to
3

Notatki

Notatka: When using arrays with pattern and replacement, the keys are processed in the order they appear in the array. This is not necessarily the same as the numerical index order. If you use indexes to identify which pattern should be replaced by which replacement, you should perform a ksort() on each array prior to calling preg_replace().

Patrz także

preg_match()

preg_replace_callback()

preg_split()

Poprzedni	Spis treści	Następny
preg_replace_callback	Początek rozdziału	preg_split