preg_replace

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

preg_replacePerform a regular expression search and replace

Опис

preg_replace(
    string|array $pattern,
    string|array $replacement,
    string|array $subject,
    int $limit = -1,
    int &$count = null
): string|array|null

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

To match an exact string, rather than a pattern, consider using str_replace() or str_ireplace() instead of this function.

Параметри

pattern

The pattern to search for. It can be either a string or an array with strings.

Several PCRE modifiers are also available.

replacement

The string or an array with strings to replace. If this parameter is a string and the pattern parameter is an array, all patterns 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 fewer elements in the replacement array than in the pattern array, any extra patterns will be replaced by an empty string.

replacement may contain references of the form \n or $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. Note that backslashes in string literals may require to be escaped.

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.

When using the deprecated e modifier, this function escapes some characters (namely ', ", \ and NULL) in the strings that replace the backreferences. This is done to ensure that no syntax errors arise from backreference usage with either single or double quotes (e.g. 'strlen(\'$1\')+strlen("$2")'). Make sure you are aware of PHP's string syntax to know exactly how the interpreted string will look.

subject

The string or an array with strings to search and replace.

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.

If the subject array is associative, keys will be preserved in the returned value.

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.

Значення, що повертаються

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 or null if an error occurred.

Помилки/виключення

Using the "\e" modifier is an error; an E_WARNING is emitted in this case.

Якщо задано хибний шаблон регулярного виразу, виведеться повідомлення рівня E_WARNING.

Приклади

Приклад #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);
?>

Поданий вище приклад виведе:

April1,2003

Приклад #2 Using indexed arrays with preg_replace()

<?php
$string
= 'The quick brown fox jumps over the lazy dog.';
$patterns = array();
$patterns[0] = '/quick/';
$patterns[1] = '/brown/';
$patterns[2] = '/fox/';
$replacements = array();
$replacements[2] = 'bear';
$replacements[1] = 'black';
$replacements[0] = 'slow';
echo
preg_replace($patterns, $replacements, $string);
?>

Поданий вище приклад виведе:

The bear black slow jumps over the lazy dog.

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

<?php
$string
= 'The quick brown fox jumps over the lazy dog.';
$patterns = array();
$patterns[0] = '/quick/';
$patterns[1] = '/brown/';
$patterns[2] = '/fox/';
$replacements = array();
$replacements[2] = 'bear';
$replacements[1] = 'black';
$replacements[0] = 'slow';
ksort($patterns);
ksort($replacements);
echo
preg_replace($patterns, $replacements, $string);
?>

Поданий вище приклад виведе:

The slow black bear jumps over the lazy dog.

Приклад #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');
?>

Поданий вище приклад виведе:

$startDate = 5/27/1999

Приклад #4 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;
?>

Приклад #5 Using the count parameter

<?php
$count
= 0;

echo
preg_replace(array('/\d/', '/\s/'), '*', 'xp 4 to', -1 , $count);
echo
$count; //3
?>

Поданий вище приклад виведе:

xp***to
3

Примітки

Зауваження:

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().

Зауваження:

When both pattern and replacement are arrays, matching rules will operate sequentially. That is, the second pattern/replacement pair will operate on the string that results from the first pattern/replacement pair, not the original string. If you want to simulate replacements operating in parallel, such as swapping two values, replace one pattern by an intermediary placeholder, then in a later pair replace that intermediary placeholder with the desired replacement.

<?php
$p
= array('/a/', '/b/', '/c/');
$r = array('b', 'c', 'd');
print_r(preg_replace($p, $r, 'a'));
// prints d
?>

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