php之str_replace详解

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本文详细解析了PHP中的字符串替换函数str_replace的用法、参数、返回值及常见例子，帮助开发者掌握字符串操作技巧。

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str_replace

(PHP 4, PHP 5)

str_replace — Replace all occurrences of the search string with the replacement string

Description

 
  mixed 
  str_replace ( 
  mixed $search , 
  mixed $replace , 
  mixed $subject [, 
  int &$count ] )
 

This function returns a string or an array with all occurrences of search in subject replaced with the givenreplace value.

If you don't need fancy replacing rules (like regular expressions), you should always use this function instead ofpreg_replace().

Parameters

If search and replace are arrays, then str_replace() takes a value from each array and uses them to search and replace on subject. If replace has fewer values than search, then an empty string is used for the rest of replacement values. If search is an array and replace is a string, then this replacement string is used for every value of search. The converse would not make sense, though.

If search or replace are arrays, their elements are processed first to last.

search

The value being searched for, otherwise known as the needle. An array may be used to designate multiple needles.

replace

The replacement value that replaces found search values. An array may be used to designate multiple replacements.

subject

The string or array being searched and replaced on, otherwise known as the haystack.

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

count

If passed, this will be set to the number of replacements performed.

Return Values

This function returns a string or an array with the replaced values.

Changelog

Version	Description
5.0.0	The `count` parameter was added.
4.3.3	The behaviour of this function changed. In older versions a bug existed when using arrays as both`search` and `replace` parameters which caused empty `search` indexes to be skipped without advancing the internal pointer on the `replace` array. This has been corrected in PHP 4.3.3, any scripts which relied on this bug should remove empty search values prior to calling this function in order to mimic the original behavior.
4.0.5	Most parameters can now be an array.

Examples

Example #1 Basic str_replace() examples

<?php
 // Provides: <body text='black'>
 $bodytag = str_replace("%body%", "black", "<body text='%body%'>");
 
 // Provides: Hll Wrld f PHP
 $vowels = array("a", "e", "i", "o", "u", "A", "E", "I", "O", "U");
 $onlyconsonants = str_replace($vowels, "", "Hello World of PHP");
 
 // Provides: You should eat pizza, beer, and ice cream every day
 $phrase  = "You should eat fruits, vegetables, and fiber every day.";
 $healthy = array("fruits", "vegetables", "fiber");
 $yummy   = array("pizza", "beer", "ice cream");
 
 $newphrase = str_replace($healthy, $yummy, $phrase);
 
 // Provides: 2
 $str = str_replace("ll", "", "good golly miss molly!", $count);
 echo $count;
 ?>

Example #2 Examples of potential str_replace() gotchas

<?php
 // Order of replacement
 $str     = "Line 1\nLine 2\rLine 3\r\nLine 4\n";
 $order   = array("\r\n", "\n", "\r");
 $replace = '<br />';
 
 // Processes \r\n's first so they aren't converted twice.
 $newstr = str_replace($order, $replace, $str);
 
 // Outputs F because A is replaced with B, then B is replaced with C, and so on...
 // Finally E is replaced with F, because of left to right replacements.
 $search  = array('A', 'B', 'C', 'D', 'E');
 $replace = array('B', 'C', 'D', 'E', 'F');
 $subject = 'A';
 echo str_replace($search, $replace, $subject);
 
 // Outputs: apearpearle pear
 // For the same reason mentioned above
 $letters = array('a', 'p');
 $fruit   = array('apple', 'pear');
 $text    = 'a p';
 $output  = str_replace($letters, $fruit, $text);
 echo $output;
 ?>