Php 使用str_replace使其仅在第一次匹配时起作用？
我想要一个版本的Php 使用str_replace使其仅在第一次匹配时起作用？,php,string,Php,String,我想要一个版本的str_replace（），它只替换$subject中第一次出现的$search。是否有一个简单的解决方案，或者我需要一个黑客解决方案？可以通过以下方式完成： 神奇之处在于可选的第四个参数[Limit]。从文件中： [限制]-可能的最大值 每种模式中每种模式的替换 主题字符串。默认值为-1（否） 限制） 但是，请参阅以获得更有效的方法（大约快3-4倍）。最简单的方法是使用正则表达式 另一种方法是使用strpos（）和substr_replace（）查找字符串的位置 但是我真的会选
str_replace（）$subject$search但是，请参阅以获得更有效的方法（大约快3-4倍）。最简单的方法是使用正则表达式 另一种方法是使用strpos（）和substr_replace（）查找字符串的位置
但是我真的会选择RegExp。没有它的版本，但是解决方案一点也不粗糙
$pos = strpos($haystack, $needle);
if ($pos !== false) {
$newstring = substr_replace($haystack, $replace, $pos, strlen($needle));
}
好处：如果您想替换最后一次出现的内容，只需使用
strrposstrpos您可以像这样轻松地滚动自己的屏幕：
function replace_first($find, $replace, $subject) {
// stolen from the comments at PHP.net/str_replace
// Splits $subject into an array of 2 items by $find,
// and then joins the array with $replace
return implode($replace, explode($find, $subject, 2));
}
function str_replace_first($search, $replace, $subject) {
$pos = strpos($subject, $search);
if ($pos !== false) {
return substr_replace($subject, $replace, $pos, strlen($search));
}
return $subject;
}
implode($replace, explode($search, $subject, 2));
function str_replace_first($search, $replace, $subject) {
return implode($replace, explode($search, $subject, 2));
}
function str_replace_limit($search, $replace, $string, $limit = 1) {
$pos = strpos($string, $search);
if ($pos === false) {
return $string;
}
$searchLen = strlen($search);
for ($i = 0; $i < $limit; $i++) {
$string = substr_replace($string, $replace, $pos, $searchLen);
$pos = strpos($string, $search);
if ($pos === false) {
break;
}
}
return $string;
}
str\u replace（）str_replace_limit（）str_replace（）str_replace（）$search$replace$subject（$string===strval（intval（strval（$string）））valid\u integer（）str\u replace\u limit（）str\u replace（）str\u replace（）str\u replace\u limit（）您可以使用：
function str_replace_once($str_pattern, $str_replacement, $string){
if (strpos($string, $str_pattern) !== false){
$occurrence = strpos($string, $str_pattern);
return substr_replace($string, $str_replacement, strpos($string, $str_pattern), strlen($str_pattern));
}
return $string;
}
从php.net中找到此示例
用法：
$string = "Thiz iz an examplz";
var_dump(str_replace_once('z','Z', $string));
输出：
ThiZ iz an examplz
这可能会稍微降低性能，但这是最简单的解决方案。根据我的测试结果，我想投票选择karim79提供的常规\u express。（我现在没有足够的声誉去投票！）
来自zombat的解决方案使用了太多的函数调用，我甚至简化了代码。我使用PHP5.4运行这两个解决方案100000次，结果如下：
$str = 'Hello abc, have a nice day abc! abc!';
$pos = strpos($str, 'abc');
$str = substr_replace($str, '123', $pos, 3);
=>1.85秒
$str = 'Hello abc, have a nice day abc! abc!';
$str = preg_replace('/abc/', '123', $str, 1);
=>1.35秒
如你所见。preg_replace的性能并不像许多人想象的那么差。因此，如果您的正则表达式不复杂，我建议使用经典的解决方案。为了扩展zombat的答案（我认为这是最好的答案），我创建了他的函数的递归版本，该函数采用了一个$limit
参数来指定要替换的出现次数
function str_replace_limit($haystack, $needle, $replace, $limit, $start_pos = 0) {
if ($limit <= 0) {
return $haystack;
} else {
$pos = strpos($haystack,$needle,$start_pos);
if ($pos !== false) {
$newstring = substr_replace($haystack, $replace, $pos, strlen($needle));
return str_replace_limit($newstring, $needle, $replace, $limit-1, $pos+strlen($replace));
} else {
return $haystack;
}
}
}
函数str\u replace\u limit（$haystack，$needle，$replace，$limit，$start\u pos=0）{
如果字符串的（$limit）
$string = 'OOO.OOO.OOO.S';
$search = 'OOO';
$replace = 'B';
//replace ONLY FIRST occurance of "OOO" with "B"
$string = substr_replace($string,$replace,0,strlen($search));
//$string => B.OOO.OOO.S
//replace ONLY LAST occurance of "OOOO" with "B"
$string = substr_replace($string,$replace,strrpos($string,$search),strlen($search))
//$string => OOO.OOO.B.S
//replace ONLY LAST occurance of "OOOO" with "B"
$string = strrev(implode(strrev($replace),explode(strrev($search),strrev($string),2)))
//$string => OOO.OOO.B.S
对于单个字符
$string[strpos($string,$search)] = $replace;
//EXAMPLE
$string = 'O.O.O.O.S';
$search = 'O';
$replace = 'B';
//replace ONLY FIRST occurance of "O" with "B"
$string[strpos($string,$search)] = $replace;
//$string => B.O.O.O.S
//replace ONLY LAST occurance of "O" with "B"
$string[strrpos($string,$search)] = $replace;
// $string => B.O.O.B.S
我想知道哪一个跑得最快，所以我测试了它们
您将在下面找到：
- 此页面上提供的所有功能的综合列表
- 每个施工的基准测试（平均执行时间超过10000次）
- 每个答案的链接（完整代码）
使用相同的设置测试所有功能：
$string = 'OOO.OOO.OOO.S';
$search = 'OOO';
$replace = 'B';
仅替换字符串中第一个出现的字符串的函数：
-
-
-
-
-
-
-
仅替换字符串中最后出现的字符串的函数：
-
-
我创建了一个简单的类来包装我们稍加修改的函数
我们的php:：str_rreplace（）函数还允许您执行一个反向的、有限的str_replace（），这在尝试仅替换字符串的最后一个X实例时非常方便
这两个例子都使用
代码修改了，所以请考虑一些旧的的注释。
感谢大家帮助我改进这一点
如果有任何问题，请与我联系，我会马上解决
因此，让我们开始：
将第一个'o'替换为'ea'，例如：
$s='I love you';
$s=str_replace_first('o','ea',$s);
echo $s;
//output: I leave you
职能：
function str_replace_first($this,$that,$s)
{
$w=strpos($s,$this);
if($w===false)return $s;
return substr($s,0,$w).$that.substr($s,$w+strlen($this));
}
此函数深受@renocor答案的启发。
它使函数多字节安全
function str_replace_limit($search, $replace, $string, $limit)
{
$i = 0;
$searchLength = mb_strlen($search);
while(($pos = mb_strpos($string, $search)) !== false && $i < $limit)
{
$string = mb_substr_replace($string, $replace, $pos, $searchLength);
$i += 1;
}
return $string;
}
function mb_substr_replace($string, $replacement, $start, $length = null, $encoding = null)
{
$string = (array)$string;
$encoding = is_null($encoding) ? mb_internal_encoding() : $encoding;
$length = is_null($length) ? mb_strlen($string) - $start : $length;
$string = array_map(function($str) use ($replacement, $start, $length, $encoding){
$begin = mb_substr($str, 0, $start, $encoding);
$end = mb_substr($str, ($start + $length), mb_strlen($str), $encoding);
return $begin . $replacement . $end;
}, $string);
return ( count($string) === 1 ) ? $string[0] : $string;
}
函数str\u replace\u limit（$search，$replace，$string，$limit）
{
$i=0；
$searchLength=mb_strlen（$search）；
而（$pos=mb_strpos（$string$
$str = 'Hello abc, have a nice day abc! abc!';
$pos = strpos($str, 'abc');
$str = substr_replace($str, '123', $pos, 3);
$str = 'Hello abc, have a nice day abc! abc!';
$str = preg_replace('/abc/', '123', $str, 1);
function str_replace_limit($haystack, $needle, $replace, $limit, $start_pos = 0) {
if ($limit <= 0) {
return $haystack;
} else {
$pos = strpos($haystack,$needle,$start_pos);
if ($pos !== false) {
$newstring = substr_replace($haystack, $replace, $pos, strlen($needle));
return str_replace_limit($newstring, $needle, $replace, $limit-1, $pos+strlen($replace));
} else {
return $haystack;
}
}
}
$string = 'OOO.OOO.OOO.S';
$search = 'OOO';
$replace = 'B';
//replace ONLY FIRST occurance of "OOO" with "B"
$string = substr_replace($string,$replace,0,strlen($search));
//$string => B.OOO.OOO.S
//replace ONLY LAST occurance of "OOOO" with "B"
$string = substr_replace($string,$replace,strrpos($string,$search),strlen($search))
//$string => OOO.OOO.B.S
//replace ONLY LAST occurance of "OOOO" with "B"
$string = strrev(implode(strrev($replace),explode(strrev($search),strrev($string),2)))
//$string => OOO.OOO.B.S
$string[strpos($string,$search)] = $replace;
//EXAMPLE
$string = 'O.O.O.O.S';
$search = 'O';
$replace = 'B';
//replace ONLY FIRST occurance of "O" with "B"
$string[strpos($string,$search)] = $replace;
//$string => B.O.O.O.S
//replace ONLY LAST occurance of "O" with "B"
$string[strrpos($string,$search)] = $replace;
// $string => B.O.O.B.S
$string = 'OOO.OOO.OOO.S';
$search = 'OOO';
$replace = 'B';
[CONTRIBUTED BY] => zombat
[OOO.OOO.OOO.S] => B.OOO.OOO.S
[AVERAGE TIME] => 0.0000062883
[SLOWER BY] => FASTEST
[CONTRIBUTED BY] => too much php
[OOO.OOO.OOO.S] => B.OOO.OOO.S
[AVERAGE TIME] => 0.0000073902
[SLOWER BY] => 17.52%
[CONTRIBUTED BY] => karim79
[OOO.OOO.OOO.S] => B.OOO.OOO.S
[AVERAGE TIME] => 0.0000077519
[SLOWER BY] => 23.27%
[CONTRIBUTED BY] => happyhardik
[OOO.OOO.OOO.S] => B.OOO.OOO.S
[AVERAGE TIME] => 0.0000082286
[SLOWER BY] => 30.86%
[CONTRIBUTED BY] => bfrohs - expanded renocor
[OOO.OOO.OOO.S] => B.OOO.OOO.S
[AVERAGE TIME] => 0.0000083342
[SLOWER BY] => 32.54%
[CONTRIBUTED BY] => renocor
[OOO.OOO.OOO.S] => B.OOO.OOO.S
[AVERAGE TIME] => 0.0000093116
[SLOWER BY] => 48.08%
[CONTRIBUTED BY] => jayoaK
[OOO.OOO.OOO.S] => B.OOO.OOO.S
[AVERAGE TIME] => 0.0000093862
[SLOWER BY] => 49.26%
[CONTRIBUTED BY] => oLinkSoftware - modified zombat
[OOO.OOO.OOO.S] => OOO.OOO.B.S
[AVERAGE TIME] => 0.0000068083
[SLOWER BY] => FASTEST
[CONTRIBUTED BY] => oLinkSoftware
[OOO.OOO.OOO.S] => OOO.OOO.B.S
[AVERAGE TIME] => 0.0000084460
[SLOWER BY] => 24.05%
<?php
class php {
/**
* str_replace() from the end of a string that can also be limited e.g. replace only the last instance of '</div>' with ''
*
* @param string $find
* @param string $replace
* @param string $subject
* @param int $replacement_limit | -1 to replace all references
*
* @return string
*/
public static function str_replace($find, $replace, $subject, $replacement_limit = -1) {
$find_pattern = str_replace('/', '\/', $find);
return preg_replace('/' . $find_pattern . '/', $replace, $subject, $replacement_limit);
}
/**
* str_replace() from the end of a string that can also be limited e.g. replace only the last instance of '</div>' with ''
*
* @param string $find
* @param string $replace
* @param string $subject
* @param int $replacement_limit | -1 to replace all references
*
* @return string
*/
public static function str_rreplace($find, $replace, $subject, $replacement_limit = -1) {
return strrev( self::str_replace(strrev($find), strrev($replace), strrev($subject), $replacement_limit) );
}
}
function str_replace_once($search, $replace, $subject) {
$pos = strpos($subject, $search);
if ($pos === false) {
return $subject;
}
return substr($subject, 0, $pos) . $replace . substr($subject, $pos + strlen($search));
}
$s='I love you';
$s=str_replace_first('o','ea',$s);
echo $s;
//output: I leave you
function str_replace_first($this,$that,$s)
{
$w=strpos($s,$this);
if($w===false)return $s;
return substr($s,0,$w).$that.substr($s,$w+strlen($this));
}
function str_replace_limit($search, $replace, $string, $limit)
{
$i = 0;
$searchLength = mb_strlen($search);
while(($pos = mb_strpos($string, $search)) !== false && $i < $limit)
{
$string = mb_substr_replace($string, $replace, $pos, $searchLength);
$i += 1;
}
return $string;
}
function mb_substr_replace($string, $replacement, $start, $length = null, $encoding = null)
{
$string = (array)$string;
$encoding = is_null($encoding) ? mb_internal_encoding() : $encoding;
$length = is_null($length) ? mb_strlen($string) - $start : $length;
$string = array_map(function($str) use ($replacement, $start, $length, $encoding){
$begin = mb_substr($str, 0, $start, $encoding);
$end = mb_substr($str, ($start + $length), mb_strlen($str), $encoding);
return $begin . $replacement . $end;
}, $string);
return ( count($string) === 1 ) ? $string[0] : $string;
}
$string = "Lorem ipsum lá lá lá";
$string[0] = "B";
echo $string;
$str = "Hello there folks!"
$str_ex = explode("there, $str, 2); //explodes $string just twice
//outputs: array ("Hello ", " folks")
$str_final = implode("", $str_ex); // glues above array together
// outputs: str("Hello folks")
/**
* Replace the first occurence of given string
*
* @param string $search a char to search in `$subject`
* @param string $replace a char to replace in `$subject`
* @param string $subject
* @return string
*
* @throws InvalidArgumentException if `$search` or `$replace` are invalid or if `$subject` is a multibytes string
*/
function str_replace_first(string $search , string $replace , string $subject) : string {
// check params
if(strlen($replace) != 1 || strlen($search) != 1) {
throw new InvalidArgumentException('$search & $replace must be char');
}elseif(mb_strlen($subject) != strlen($subject)){
throw new InvalidArgumentException('$subject is an multibytes string');
}
// search
$pos = strpos($subject, $search);
if($pos === false) {
// not found
return $subject;
}
// replace
$subject[$replace] = $subject;
return $subject;
}
<?php
echo replaceFirstMatchedChar("&", "?", "/property/details&id=202&test=123#tab-6");
function replaceFirstMatchedChar($searchChar, $replaceChar, $str)
{
for ($i = 0; $i < strlen($str); $i++) {
if ($str[$i] == $searchChar) {
$str[$i] = $replaceChar;
break;
}
}
return $str;
}
$str = "/property/details&id=202&test=123#tab-6p";
$position = strpos($str,"&");
echo substr_replace($str,"?",$position,1);