(PHP 4, PHP 5, PHP 7, PHP 8)
preg_replace —Perform a regular expression search and replace
$pattern,$replacement,$subject,$limit = -1,&$count =null Searchessubject for matches topattern and replaces them withreplacement.
To match an exact string, rather than a pattern, consider usingstr_replace() orstr_ireplace() instead of this function.
patternThe pattern to search for. It can be either a string or an array with strings.
SeveralPCRE modifiers are also available.
replacement The string or an array with strings to replace. If this parameter is a string and thepattern parameter is an array, all patterns will be replaced by that string. If bothpattern andreplacement parameters are arrays, eachpattern will be replaced by thereplacement counterpart. If there are fewer elements in thereplacement array than in thepattern array, any extrapatterns will be replaced by an empty string.
replacement may contain references of the form\n or$n, with the latter form being the preferred one. Every such reference will be replaced by the text captured by then'th parenthesized pattern.n can be from 0 to 99, and\0 or$0 refers to the text matched by the whole pattern. Opening parentheses are counted from left to right (starting from 1) to obtain the number of the capturing subpattern. Note that backslashes instring literals may require to be escaped.
When working with a replacement pattern where a backreference is immediately followed by another number (i.e.: placing a literal number immediately after a matched pattern), you cannot use the familiar\1 notation for your backreference.\11, for example, would confusepreg_replace() since it does not know whether you want the\1 backreference followed by a literal1, or the\11 backreference followed by nothing. In this case the solution is to use${1}1. This creates an isolated$1 backreference, leaving the1 as a literal.
When using the deprecatede 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'sstring syntax to know exactly how the interpreted string will look.
subjectThe string or an array with strings to search and replace.
Ifsubject is an array, then the search and replace is performed on every entry ofsubject, and the return value is an array as well.
If thesubject array is associative, keys will be preserved in the returned value.
limit The maximum possible replacements for each pattern in eachsubject string. Defaults to-1 (no limit).
countIf specified, this variable will be filled with the number of replacements done.
preg_replace() returns an array if thesubject parameter is an array, or a string otherwise.
If matches are found, the newsubject will be returned, otherwisesubject will be returned unchanged ornull if an error occurred.
Using the "\e" modifier is an error; anE_WARNING is emitted in this case.
If the regex pattern passed does not compile to a valid regex, anE_WARNING is emitted.
Example #1 Using backreferences followed by numeric literals
<?php
$string='April 15, 2003';
$pattern='/(\w+) (\d+), (\d+)/i';
$replacement='${1}1,$3';
echopreg_replace($pattern,$replacement,$string);
?>The above example will output:
April1,2003
Example #2 Using indexed arrays withpreg_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';
$replacements[0] ='slow';
echopreg_replace($patterns,$replacements,$string);
?>The above example will output:
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($replacements);
echopreg_replace($patterns,$replacements,$string);
?>The above example will output:
The slow black bear jumps over the lazy dog.
Example #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 =');
echopreg_replace($patterns,$replace,'{startDate} = 1999-5-27');
?>The above example will output:
$startDate = 5/27/1999
Example #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;
?>Example #5 Using thecount parameter
<?php
$count=0;
echopreg_replace(array('/\d/','/\s/'),'*','xp 4 to', -1,$count);
echo$count;//3
?>The above example will output:
xp***to3
Note:
When using arrays with
patternandreplacement, the keys are processed in the order they appear in the array. This isnot necessarily the same as the numerical index order. If you use indexes to identify whichpatternshould be replaced by whichreplacement, you should perform aksort() on each array prior to callingpreg_replace().
Note:
When both
patternandreplacementare arrays, matching rules will operate sequentially. That is, the secondpattern/replacementpair will operate on the string that results from the firstpattern/replacementpair, 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
?>
Because i search a lot 4 this:The following should be escaped if you are trying to match that character\ ^ . $ | ( ) [ ]* + ? { } ,Special Character Definitions\ Quote the next metacharacter^ Match the beginning of the line. Match any character (except newline)$ Match the end of the line (or before newline at the end)| Alternation() Grouping[] Character class* Match 0 or more times+ Match 1 or more times? Match 1 or 0 times{n} Match exactly n times{n,} Match at least n times{n,m} Match at least n but not more than m timesMore Special Character Stuff\t tab (HT, TAB)\n newline (LF, NL)\r return (CR)\f form feed (FF)\a alarm (bell) (BEL)\e escape (think troff) (ESC)\033 octal char (think of a PDP-11)\x1B hex char\c[ control char\l lowercase next char (think vi)\u uppercase next char (think vi)\L lowercase till \E (think vi)\U uppercase till \E (think vi)\E end case modification (think vi)\Q quote (disable) pattern metacharacters till \EEven More Special Characters\w Match a "word" character (alphanumeric plus "_")\W Match a non-word character\s Match a whitespace character\S Match a non-whitespace character\d Match a digit character\D Match a non-digit character\b Match a word boundary\B Match a non-(word boundary)\A Match only at beginning of string\Z Match only at end of string, or before newline at the end\z Match only at end of string\G Match only where previous m//g left off (works only with /g)You can only use numeric backreferences in the replacement string, but not named ones:<?phpechopreg_replace('#(\d+)#','\1 $1 ${1}','123');// 123 123 123echopreg_replace('#(?<digits>\d+)#','\digits $digits ${digits}','123');// \digits $digits ${digits}?>To use named backreferences, you have to use preg_replace_callback:<?phpechopreg_replace_callback('#(?<digits>\d+)#', function($m){ return"$m[1]$m[digits]{$m['digits']}";},'123');// 123 123 123echopreg_replace_callback('#(?<digits>\d+)#', fn($m) =>"$m[1]$m[digits]{$m['digits']}",'123');// 123 123 123?>Seehttps://bugs.php.net/bug.php?id=81469To split Pascal/CamelCase into Title Case (for example, converting descriptive class names for use in human-readable frontends), you can use the below function:<?phpfunctionexpandCamelCase($source) { returnpreg_replace('/(?<!^)([A-Z][a-z]|(?<=[a-z])[^a-z]|(?<=[A-Z])[0-9_])/',' $1',$source);}?>Before: ExpandCamelCaseAPIDescriptorPHP5_3_4Version3_21BetaAfter: Expand Camel Case API Descriptor PHP 5_3_4 Version 3_21 BetaHow to replace all comments inside code without remove crln = \r\n or cr \r each line?<?php$txt_target=<<<t1this;// dsdsds nope /* ok */is;huge/*text bla*/ /*bla*/t1;/*=======================================================================expected result:=======================================================================this; nopeis;huge=======================================================================visualizing in a hex viewer .. to_check_with_a_hex_viewer.txt ... t h i s ; LF TAB n o p e CR LF CR LF i s ; h u g e CR LF74 68 69 73 3b 0a 09 6e 6f 70 65 0d 0a 0d 0a 69 73 3b 68 75 67 65 0d 0aI used F3 (viewer + options 3: hex) in mythical TOTAL COMMANDER!=======================================================================*/echo'<hr><pre>';echo$txt_target;echo'</pre>';// a single line '//' comments$txt_target=preg_replace('![ \t]*//.*[ \t]*!','',$txt_target);// /* comment */$txt_target=preg_replace('/\/\*([^\/]*)\*\/(\s+)/smi','',$txt_target);echo'<hr><pre>';echo$txt_target;echo'</pre><hr>';file_put_contents('to_check_with_a_hex_viewer.txt',$txt_target);?>Be aware that when using the "/u" modifier, if your input text contains any bad UTF-8 code sequences, then preg_replace will return an empty string, regardless of whether there were any matches.This is due to the PCRE library returning an error code if the string contains bad UTF-8.From what I can see, the problem is, that if you go straight and substitute all 'A's wit 'T's you can't tell for sure which 'T's to substitute with 'A's afterwards. This can be for instance solved by simply replacing all 'A's by another character (for instance '_' or whatever you like), then replacing all 'T's by 'A's, and then replacing all '_'s (or whatever character you chose) by 'A's:<?php$dna="AGTCTGCCCTAG";echostr_replace(array("A","G","C","T","_","-"), array("_","-","G","A","T","C"),$dna);//output will be TCAGACGGGATC?>Although I don't know how transliteration in perl works (though I remember that is kind of similar to the UNIX command "tr") I would suggest following function for "switching" single chars:<?phpfunctionswitch_chars($subject,$switch_table,$unused_char="_") { foreach ($switch_tableas$_1=>$_2) {$subject=str_replace($_1,$unused_char,$subject);$subject=str_replace($_2,$_1,$subject);$subject=str_replace($unused_char,$_2,$subject); } return$subject;}echoswitch_chars("AGTCTGCCCTAG", array("A"=>"T","G"=>"C"));//output will be TCAGACGGGATC?>Below is a function for converting Hebrew final characters to theirnormal equivelants should they appear in the middle of a word.The /b argument does not treat Hebrew letters as part of a word,so I had to work around that limitation.<?php$text="עברית מבולגנת";functionhebrewNotWordEndSwitch($from,$to,$text) {$text=preg_replace('/'.$from.'([א-ת])/u','$2'.$to.'$1',$text); return$text;}do {$text_before=$text;$text=hebrewNotWordEndSwitch("ך","כ",$text);$text=hebrewNotWordEndSwitch("ם","מ",$text);$text=hebrewNotWordEndSwitch("ן","נ",$text);$text=hebrewNotWordEndSwitch("ף","פ",$text);$text=hebrewNotWordEndSwitch("ץ","צ",$text);} while ($text_before!=$text);print$text;// עברית מסודרת!?>The do-while is necessary for multiple instances of letters, suchas "אנני" which would start off as "אןןי". Note that there's still theproblem of acronyms with gershiim but that's not a difficult oneto solve. The code is in use athttp://gibberish.co.il which you canuse to translate wrongly-encoded Hebrew, transliterize, and someother Hebrew-related functions.To ensure that there will be no regular characters at the end of aword, just convert all regular characters to their final forms, thenrun this function. Enjoy!If you would like to remove a tag along with the text inside it then use the following code.<?phppreg_replace('/(<tag>.+?)+(<\/tag>)/i','',$string);?>example<?php $string='<span>55 PKR</span>';?><?php$string=preg_replace('/(<span>.+?)+(<\/span>)/i','',$string);?>This will results a null or empty string.<?php$string='My String <span>55 PKR</span>';$string=preg_replace('/(<span>.+?)+(<\/span>)/i','',$string);?>This will results a " My String"A delimiter can be any ASCII non-alphanumeric, non-backslash, non-whitespace character: !"#$%&'*+,./:;=?@^_`|~- and ({[<>]})Sample for replacing bracketed short-codesThe used short-codes are purely used for educational purposes for they could be shorter as in 'italic' to 'i' or 'bold' to 'b'.Sample text----This sample shows how to have [italic]italic[/italic], [bold]bold[/bold] and [underline]underlined[/underline] and [strikethrough]striked[/striketrhough] text. with this function:<?phpfunctiontextDecoration($html){$patterns= ['/\[(italic)\].*?\[\/\1\] ?/','/\[(bold)\].*?\[\/\1\] ?/','/\[(underline)\].*?\[\/\1\] ?/'];$replacements= ['<i>$1</i>','<strong>$1</strong>','<u>$1</u>']; returnpreg_replace($patterns,$replacements,$html);}$html=textDecoration($html);echo$html;// or return?>results in:----This sample shows how to have <i>italic</i>, <b>bold</b> and <u>underlined</u> and [strikethrough]striked[/striketrhough] text.Notice!There is no [strikethrough]striked[/striketrhough] fallback in the patterns and replacements array