substr_replace

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

substr_replace — 替换字符串的子串

说明

substr_replace() 在字符串 string 的副本中将由 offset 和可选的 length 参数限定的子字符串使用 replace 进行替换。

参数

string

输入字符串。

可以提供 array 类型的 string，会依次替换出现的字符串。在这种情况下，replace、offset 和 length 参数可以作为标量值依次提供给每个输入字符串，或者作为 array 提供，然后数组元素将会相应的用于每个输入字符串。

replace

替换字符串。

offset

如果 offset 为非负数，替换将从 string 的 offset 位置开始。

如果 offset 为负数，替换将从 string 的倒数第 offset 个位置开始。

length

如果设定了这个参数并且为正数，表示 string 中被替换的子字符串的长度。如果设定为负数，它表示待替换的子字符串结尾处距离 string 末端的字符个数。如果没有提供此参数，那么它默认为 strlen( string )（字符串的长度）。当然，如果 length 为 0，那么这个函数的功能为将 replace 插入到 string 的 offset 位置处。

返回值

返回结果字符串。如果 string 是个数组，那么也将返回一个数组。

更新日志

版本	说明
8.0.0	`length` 现在允许为 null。

示例

示例 #1 substr_replace() 示例

<?php
$var = 'ABCDEFGH:/MNRPQR/';
echo "Original: $var<hr />\n";

/* 这两个例子使用 “bob” 替换整个 $var。*/
echo substr_replace($var, 'bob', 0) . "<br />\n";
echo substr_replace($var, 'bob', 0, strlen($var)) . "<br />\n";

/* 将 “bob” 插入到 $var 的开头处。*/
echo substr_replace($var, 'bob', 0, 0) . "<br />\n";

/* 下面两个例子使用 “bob” 替换 $var 中的 “MNRPQR”。*/
echo substr_replace($var, 'bob', 10, -1) . "<br />\n";
echo substr_replace($var, 'bob', -7, -1) . "<br />\n";

/* 从 $var 中删除 “MNRPQR”。*/
echo substr_replace($var, '', 10, -1) . "<br />\n";
?>

示例 #2 一次性使用 substr_replace() 替换多个字符串

<?php
$input = array('A: XXX', 'B: XXX', 'C: XXX');

// 简单用例：将每个字符串使用 YYY 替换为 XXX。
echo implode('; ', substr_replace($input, 'YYY', 3, 3))."\n";

// 更复杂的情况，每种替换都不同。
$replace = array('AAA', 'BBB', 'CCC');
echo implode('; ', substr_replace($input, $replace, 3, 3))."\n";

// 每次替换的字符数不同。
$length = array(1, 2, 3);
echo implode('; ', substr_replace($input, $replace, 3, $length))."\n";
?>

以上示例会输出：

A: YYY; B: YYY; C: YYY
A: AAA; B: BBB; C: CCC
A: AAAXX; B: BBBX; C: CCC

注释

注意: 此函数可安全用于二进制对象。

参见

str_replace() - 子字符串替换
substr() - 返回字符串的子串
字符串访问与修改

改进此页面

了解如何改进此页面 • 提交拉取请求 • 报告一个错误

＋添加备注

用户贡献的备注 32 notes

down

elloromtz at gmail dot com ¶

14 years ago

It's worth noting that when start and length are both negative -and- the length is less than or equal to start, the length will have the effect of being set as 0.



<?php

substr_replace('eggs','x',-1,-1); //eggxs

substr_replace('eggs','x',-1,-2); //eggxs

substr_replace('eggs','x',-1,-2); //eggxs

?>



Same as: 

<?php

substr_replace('eggs','x',-1,0); //eggxs

?>



<?php

substr_replace('huevos','x',-2,-2); //huevxos

substr_replace('huevos','x',-2,-3); //huevxos

substr_replace('huevos','x',-2,-3); //huevxos

?>



Same as: 

<?php

substr_replace('huevos','x',-2,0); //huevxos

?>



Another note, if length is negative and start offsets the same position as length, length (yet again) will have the effect as being set as 0. (Of course, as mentioned in the manual, when length is negative it actually represents the position before it)



<?php

substr_replace('abcd', 'x', 0, -4); //xabcd

?>



Same as: 

<?php

substr_replace('abcd','x',0,0); //xabcd

?>



<?php

substr_replace('abcd', 'x', 1, -3); //axbcd

?>



Same as:

<?php

substr_replace('abcd', 'x', 1, 0); //axbcd

?>

down

shaman_master at list dot ru ¶

4 years ago

Add prefix to strings:
<?php
substr_replace($strings, '_prefix', 0, 0);
?>
Add suffix/postfix to strings:
<?php
substr_replace($strings, '_suffix', array_map('strlen', $strings), 0);
?>

down

billg AT microsoft.com ¶

15 years ago

Forget all of the mb_substr_replace() implementations mentioned in this page, they're all buggy.

Here is a version that mimics the behavior of substr_replace() exactly:

<?php

if (function_exists('mb_substr_replace') === false)
{
    function mb_substr_replace($string, $replacement, $start, $length = null, $encoding = null)
    {
        if (extension_loaded('mbstring') === true)
        {
            $string_length = (is_null($encoding) === true) ? mb_strlen($string) : mb_strlen($string, $encoding);
            
            if ($start < 0)
            {
                $start = max(0, $string_length + $start);
            }
            
            else if ($start > $string_length)
            {
                $start = $string_length;
            }
            
            if ($length < 0)
            {
                $length = max(0, $string_length - $start + $length);
            }
            
            else if ((is_null($length) === true) || ($length > $string_length))
            {
                $length = $string_length;
            }
            
            if (($start + $length) > $string_length)
            {
                $length = $string_length - $start;
            }
            
            if (is_null($encoding) === true)
            {
                return mb_substr($string, 0, $start) . $replacement . mb_substr($string, $start + $length, $string_length - $start - $length);
            }
            
            return mb_substr($string, 0, $start, $encoding) . $replacement . mb_substr($string, $start + $length, $string_length - $start - $length, $encoding);
        }
        
        return (is_null($length) === true) ? substr_replace($string, $replacement, $start) : substr_replace($string, $replacement, $start, $length);
    }
}

?>

down

eblejr AT phrebh DOT com ¶

16 years ago

PHP version of Java's removeCharAt() function:

<?php
function removeCharAt($str, $int){
  return substr_replace($str,"",$int,1);
}
?>

down

danieldoorduin at hotmail dot com ¶

19 years ago

Using substr_replace() can be avoided by using substr() instead:

<?
$string = substr($string, 0, $position_needle).$replace.substr($string, $position_needle+$length_needle);
?>

This can be useful when you need to replace parts of multibyte strings like strings encoded with utf-8. There isn't a multibute variant for substr_replace(), but for php substr() there is mb_substr(). For more information on multibyte strings see http://nl3.php.net/manual/en/ref.mbstring.php

down

ivijan dot stefan at gmail dot com ¶

10 years ago

I have a little function that works like substr_replace ()  what I use for some purpose. Maybe someone needs it.

<?php
function putinplace($string=NULL, $put=NULL, $position=false)
{
    $d1=$d2=$i=false;
    $d=array(strlen($string), strlen($put));
    if($position > $d[0]) $position=$d[0];
    for($i=$d[0]; $i >= $position; $i--) $string[$i+$d[1]]=$string[$i];
    for($i=0; $i<$d[1]; $i++) $string[$position+$i]=$put[$i];
    return $string;
}

// Explanation
$string='My dog dont love postman'; // string
$put="'"; // put ' on position
$position=10; // number of characters (position)
print_r( putinplace($string, $put, $position) ); 
?>

RESULT: My dog don't love postman

This is a small powerful function that performs its job flawlessly.

down

kalim dot fleet at gmail dot com ¶

15 years ago

This will truncate a longer string to a smaller string of specified length while replacing the middle portion with a separator exactly in the middle.

<?php

$longString = 'abcdefghijklmnopqrstuvwxyz0123456789z.jpg';
$separator = '/.../';
$separatorlength = strlen($separator) ;
$maxlength = 25 - $separatorlength;
$start = $maxlength / 2 ;
$trunc =  strlen($longString) - $maxlength;

echo substr_replace($longString, $separator, $start, $trunc);

//prints "abcdefghij/.../56789z.jpg"

?>

down

bkline at rksystems dot com ¶

5 years ago

I imagine the description of the parameters really means "number of bytes" where it says "number of characters" (confirmed by testing).

down

juichenieder-phnet at yahoo dot co dot uk ¶

15 years ago

I've just taken a look at the post by ntoniazzi and I have a very small correction to make.

In the second if statement, it should be a triple equals, so:

<?php if ($length === null) ?>

It requires the triple equals, for the case of pure insertion, where $length = 0, the double equals, will catch this, causing the string to be cut short.  I hope this helps someone.

down

Hayley Watson ¶

7 years ago

See array_splice if you want to do this sort of thing to an array.

down

William Barry ¶

16 years ago

I recently ran across a situation where I need to strip a heavily nested html list such that only the top level was preserved.  I started with a regular expression solution, but found that I kept matching the wrong closing ul with an outer opening ul.

This was my alternative solution, and it seems to work well:

<?php

function stripNestedLists($str)
{
    $str2 = $str;
    $lastStr = $str2;
    
    do
    {
        // Find the first closing ul
        $cul = strpos($str2, '</ul>');
        $ul = 0;
        $lastUL = 0;
        do
        {
            // Find the next opening ul
            $lastUL = $ul;
            $ul = strpos($str2, '<ul', $ul+1);
        }
        while ($ul !== false && $ul < $cul);
    
        $lastStr = $str2;
        $str2 = substr_replace($str2, '', $lastUL, $cul-$lastUL+5);
        $str2 = trim($str2);
    }
    while (strlen($str2) > 0);
    
    return $lastStr;
}

?>

Hope this helps someone.

down

klaas at group94 dot com ¶

22 years ago

THE DOT DOT DOT ISSUE

PROBLEM:
You want to abbreviate a string.
E.g. You want "BritneySpears" to show as "BritneySpe...", being only the ten first characters followed by "..."

SOLUTION:
<?
$oRIGINAL = "BritneySpears";
$sHORTER = substr_replace($oRIGINAL, '...', 10);
echo ($sHORTER);
?>

This will result in BritneySpe...

down

alishahnovin at hotmail dot com ¶

17 years ago

I like the truncate function below...however, I found a few issues. Particularly if you have content that may have any kind of punctuation in it (?, !, ?!?, --, ..., .., ;, etc.)

The older function would end up looking like "blah blah?..." or "blah blah,..." which doesn't look so nice to me...

Here's my fix. It removes all trailing punctuation (that you include in the $punctuation string below) and then adds an ellipse. So even if it has an ellipse with 3 dots, 2 dots, 4 dots, it'll be removed, then re-added.

<?php
function truncate($text,$numb,$etc = "...") {
$text = html_entity_decode($text, ENT_QUOTES);
if (strlen($text) > $numb) {
$text = substr($text, 0, $numb);
$text = substr($text,0,strrpos($text," "));

$punctuation = ".!?:;,-"; //punctuation you want removed

$text = (strspn(strrev($text),  $punctuation)!=0)
        ?
        substr($text, 0, -strspn(strrev($text),  $punctuation))
        :
$text;

$text = $text.$etc;
}
$text = htmlentities($text, ENT_QUOTES);
return $text;
}
?>

I also needed a sort of "middle" truncate. The above function truncates around the end, but if you want to truncate around the middle (ie "Hello this is a long string." --> "Hello this ... long string.") you can use this (requires the truncate function):

<?php
function mtruncate($text, $numb, $etc = " ... ") {
    $first_part = truncate(truncate($text, strlen($text)/2, ""), $numb/2, "");
    $second_part = truncate(strrev(truncate(strrev($text), strlen($text)/2, "")), $numb/2, "");
    return $first_part.$etc.$second_part;
}
?>

down

Guru Evi ¶

19 years ago

If your string is not long enough to meet what you specify in start and length then the replacement string is added towards the end of the string.

I wanted to replace the end of the string with ... if the string was too long to display (for instance article preview on a website). The problem was that my string was sometimes not that long and it still added the replacement string. So I wrote a function to replace substr_replace in my website:

function add_3dots($string,$repl,$start,$limit) {
    if(strlen($string) > $limit) {
        return substr_replace(strip_tags($string),$repl,$start,$limit);
    } else {
        return $string;
    };
};

I use strip_tags to strip out the HTML otherwise you might get a screwed up HTML (when a tags open in the string, but because you cut-off it doesn't)

down

hermes at andycostell dot com ¶

19 years ago

I suggest changing the function suggested by Guru Evi slightly. I found that it doesn't work as written here.

Original:
function add_3dots($string,$repl,$start,$limit) {
   if(strlen($string) > $limit) {
       return substr_replace(strip_tags($string),$repl,$start,$limit);
   } else {
       return $string;
   };
};

I suggest:
function add_3dots($string,$repl,$limit) {
       if(strlen($string) > $limit) {
           return substr_replace(strip_tags($string),$repl,$limit-strlen($repl));
       } else {
           return $string;
       }
    }

Usage:

$max_length=10;//the max number of characters you want to display
$too_long_string="BLAH BLAH BLAH BLAH BLAH etc.";//the string you want to shorten (if it's longer than the $limit)
$shorter_string=add_3_dots($too_long_string,"...",$max_length);

down

yeyijelud at amadamus dot com ¶

6 years ago

First Example can be simplified =>

 $input = array('A: XXX', 'B: XXX', 'C: XXX');

 substr_replace($input, 'YYY', -3);

output: Array ( [0] => A: YYY [1] => B: YYY [2] => C: YYY )

down

meg dot phillips91 at gmail dot com ¶

4 years ago

This may be obvious to others, but I just spent hours and my feeble brain only caught up to it after a long break. 

If you are looping through a string which has multiple substrings that need to be replaced, you have to add an offset factor to each original offset before you replaced any strings. Here is a real world example: 

From draft.js we get paragraphs with multiple links designated only with offset, anchor text length, url, target. So each anchor text must be wrapped in the <a href="url" target="target">anchortext</a> to save proper content in the database. 

Here is the implementation of offset factor:

 $offset_factor = 0;

 foreach($content->links->links as $index=>$link){
            $replacement = '<a href="'.$link->href.'"  target="$link->target">'.$link->anchorText.'</a>';
            $new_offset = $link->offset + $offset_factor;
            $newtext = \substr_replace($content->text, $replacement, $new_offset, $link->length);

            //now we reset the original paragraph text with newtext
            $content->text = $newtext;
           
            //calculate the new offset by calculating the difference in replacement length and original length and add that to the offset_factor
            $additional_characters = strlen($replacement) - $link->length;
            $offset_factor =  $offset_factor + $additional_characters;
        }

I hope this helps a noobie :) If there is another easier way, I would love to hear about it.

down

nospam at nospam dot com ¶

8 years ago

<?php

// shortens a long string to a max length while inserting a string into the exact middle
function strShorten($str, $maxlen = 10, $insert = '/.../') {
  if ($str && !is_array($str)) { // valid string
    if ($maxlen && is_numeric($maxlen) && $maxlen < strlen($str)) { // string needs shortening
      if ($insert && ($ilen = strlen($insert))) { // insert string and length
        if ($ilen >= $maxlen) { // insert string too long so use default insert
          $insert = '**'; // short default so works even when a very small $maxlen
          $ilen = 2;
        }
      }
      $chars = $maxlen - $ilen; // number of $str chars to keep
      $start = ceil($chars/2); // position to start cutting
      $end = floor($chars/2); // position from end to stop cutting
      return substr_replace($str, $insert, $start, -$end); // first.insert.last
    } else { // string already short enough
      return $str; // return original string
    }
  }
}

echo strShorten('123456789', 6, ''); // outputs 123789
echo strShorten('123456789', 6, '-'); // outputs 123-89
echo strShorten('123456789', 6, 'longstring'); // outputs 12**89
echo strShorten('abcdefghijklmnopqrstuvwxyz', 10, '..'); // outputs abcd..wxyz
echo strShorten('abcdefghijklmnopqrstuvwxyz'); // outputs abc/.../yz

?>

down

NiX0n at fragfest dot cx ¶

16 years ago

The preemptive test to see if $string is "too long" shouldn't add strlen($replacement) to $max.  $max should represent the absolute maximum length of string returned.  The size of the $replacement is irrelevant in that determination.

The rest of the function (unchanged below) operates as defined above.  Meaning, the size of the $replacement is subtracted from the $max, so that the returned string is exactly the length of $max.

<?php
function truncate($string, $max = 20, $replacement = '')
{
    if (strlen($string) <= $max)
    {
        return $string;
    }
    $leave = $max - strlen ($replacement);
    return substr_replace($string, $replacement, $leave);
}
?>

down

jaimthorn at yahoo dot com ¶

16 years ago

I recently needed a routine that would remove the characters in one string from another, like the regex

<?php
   $result = preg_replace("/[$chars]/", "", $string);
?>

and I needed it to be fast, and accept pretty much all input.  The regex above won't work when strlen($chars) == 0.  I came up with this, admittedly pretty horrible-looking code, that is quite fast:

<?php

function RemoveChars($string, $chars)
{
    return isset($chars{0}) ? str_replace($chars{0}, "", strtr($string, $chars, str_pad($chars{0}, strlen($chars), $chars{0}))) : $string;
}

?>

According to my own measurements, the regex in ONLY faster for when strlen($chars) == 1; for longer strings, my routine is faster.  What does it do?  Let's say you want to remove the period, the comma and the exclamation mark from a string, like so:
$result = RemoveChars("Isn't this, like, totally neat..!?", ".?!");
The str_pad function creates a string equal in length to the string that contains the character to be removed, but consisting only of the first character of that string:
The input is ".,!"
The output is "..."
The strtr function translates all characters in the string-to-be-processed ("Isn't this...") that also occur in the input (".,!") to the characters in the same position in the output ("...").  In other words:
Isn't this, like, totally neat..!?
becomes
Isn't this. like. totally neat....
Finally, the first character from the input (".,!") which happens to be, again, the period, is removed from that string by the str_replace call:
Isn't this like totally neat?
The function needs to check is $chars has at least one character, or else the str_pad function will fail.  If it's empty, then the unprocessed string is returned.

down

chuayw2000 at hotmail dot com ¶

18 years ago

I don't know if this function is multibyte safe but I've written a function that will do the same in multibyte mode.

<?php
//Check to see if it exists in case PHP has this function later
if (!function_exists("mb_substr_replace")){
   //Same parameters as substr_replace with the extra encoding parameter.
    function mb_substr_replace($string,$replacement,$start,$length=null,$encoding = null){
        if ($encoding == null){
            if ($length == null){
                return mb_substr($string,0,$start).$replacement;
            }
            else{
                return mb_substr($string,0,$start).$replacement.mb_substr($string,$start + $length);
            }
        }
        else{
            if ($length == null){
                return mb_substr($string,0,$start,$encoding).$replacement;
            }
            else{
                return mb_substr($string,0,$start,$encoding). $replacement. mb_substr($string,$start + $length,mb_strlen($string,$encoding),$encoding);
            }
        }
    }
}
?>

down

dmron ¶

20 years ago

Regarding "...", even the short functions are too long and complicated, and there's no need to use substr_replace. substr() works better and is  way faster prior to 4.3.5 as the below poster stated.

function shorten( $str, $num = 100 ) {
  if( strlen( $str ) > $num ) $str = substr( $str, 0, $num ) . "...";
  return $str;
}

down

geniusdex ( at ) brz ( dot ) nu ¶

20 years ago

This is my version of making dotted strings:

<?php
function dot($str, $len, $dots = "...") {
    if (strlen($str) > $len) {
        $dotlen = strlen($dots);
        substr_replace($str, $dots, $len - $dotlen);
    }
}
?>

down

david at ethinkn dot com ¶

21 years ago

Here is a simple function to shorten a string and add an ellipsis

<?php

/**
 * truncate() Simple function to shorten a string and add an ellipsis
 * 
 * @param string $string Origonal string
 * @param integer $max Maximum length
 * @param string $rep Replace with... (Default = '' - No elipsis -)
 * @return string
 * @author David Duong
 **/
function truncate ($string, $max = 50, $rep = '') {
    $leave = $max - strlen ($rep);
    return substr_replace($string, $rep, $leave);
} 

echo truncate ('akfhslakdhglksjdgh', 10, '...');
// Returns akfhsla... (10 chrs)

?>

down

mrbrown8 at juno dot com ¶

23 years ago

Just to add to the examples, if replacement is longer than length, only the length number of chars are removed from string and all of replacement is put in its place, and therefor strlen($string) is inreased.



$var = 'ABCDEFGH:/MNRPQR/';

/*  Should return ABCDEFGH:/testingRPQR/   */

echo substr_replace ($var, 'testing', 10, 2);

down

-1

den dot gierling at web dot de ¶

14 years ago

My problem was that substr_replace() always added $replacement, so i wrote my own function.
This function only adds $replacement, if substr() took action.
The parameter $length is optional - like substr()'s.
Or I was too stupid using $start and $length...

<?php
function substr_replace_provided($string,$replacement,$start,$length=NULL)
{
    $tmp=substr($string,$start,$length);
    if($string!==$tmp) {
        $string = $tmp.$replacement;
    }
    return $string;
}
?>

down

-1

Thijs Wijnmaalen (thijs[at]nllinux.nl) ¶

20 years ago

I wrote a function that you can use for example in combination with a search script to cut off the articles that are too long.

<?php
function substr_index($text, $maxChars = 20, $splitter
= '...') {

$theReturn = $text;
$lastSpace = false;

if (strlen($text) > $maxChars) {
$theReturn = substr($text, 0, $maxChars - 1);

if (in_array(substr($text, $maxChars - 1, 1),
array(' ', '.', '!', '?'))) {
$theReturn .= substr($text, $maxChars, 1);
} else {
$theReturn = substr($theReturn, 0, $maxChars -
strlen($splitter));
$lastSpace = strrpos($theReturn, ' ');

if ($lastSpace !== false) {
$theReturn = substr($theReturn, 0, $lastSpace);
}

if (in_array(substr($theReturn, -1, 1), array(','))) {
$theReturn = substr($theReturn, 0, -1);
}
$theReturn .= $splitter;
}
}
return $theReturn;
}
?>

down

-2

spcl dot delivery at gmail dot com ¶

16 years ago

the version of my predecessor will add $rep even if the string is shorter than max. fixed version:



<?php

function truncate($string, $max = 20, $rep = '')

{

    if (strlen($string) <= ($max + strlen($rep)))

    {

        return $string;

    }

    $leave = $max - strlen ($rep);

    return substr_replace($string, $rep, $leave);

}

?>



To preserve the filename extension you can call it like this:



truncate([filename], 30, '...' . end(explode('.', [filename])))

down

-4

Anonymous ¶

23 years ago

If you would like to remove characters from the start or end of a string, try the substr() function.



For example, to remove the last three characters from a string:

$string = "To be or not to be.";

$string = substr ($string, 0, -3);

down

-5

blessador at gmail dot com ¶

11 years ago

<?php
$price = "12000";
$price = substr_replace ($price, ',', -3, 0)";
?> 

ensure to remove the double quot  " at the end of substr_replace ($price, ',', -3, 0)" in the above  code to avoid error.

down

-5

thomasNOSPAM at sportentranceNOSPAM dot com ¶

22 years ago

To abbreviate links into '...' if they outreach a certain amount of space; use the preg_replace function instead.

For instance you grabbed the headlines of a news site for use on your own page and the lines are to long:

asuming the raw material is stored in $unedited;

$edited = preg_replace("/(>)([[:print:]]{52,})(<)/e", "'\\1'.substr_replace('\\2 ', '...', '48').'\\3'", $unedited);
echo $edited;

This will shorten strings longer than 52 characters into 51 characters, with the last being three dots...

down

-4

olav at schettler dot net ¶

9 years ago

Please note that the function array_slice(), which has a similar functionality but for arrays rather than for strings, has its parameters in a different order.