php从第0个位置替换第一次出现的字符串

I want to search and replace the first word with another in php like as follows:

我想在php中搜索并替换第一个单词，如下所示：

$str="nothing inside";

Replace 'nothing' to 'something' by search and replace without using substr

通过搜索将'nothing'替换为'something'，并在不使用substr的情况下替换

output should be: 'something inside'

输出应该是：'里面的东西'

8 个解决方案

#1

Use preg_replace() with a limit of 1:

使用限制为1的preg_replace（）：

preg_replace('/nothing/', 'something', $str, 1);

Replace the regular expression /nothing/ with whatever string you want to search for. Since regular expressions are always evaluated left-to-right, this will always match the first instance.

将正则表达式/ nothing /替换为您要搜索的任何字符串。由于正则表达式始终从左到右进行计算，因此始终与第一个实例匹配。

#2

on the man page for str_replace (http://php.net/manual/en/function.str-replace.php) you can find this function

在str_replace的手册页（http://php.net/manual/en/function.str-replace.php）上你可以找到这个函数

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;
}

usage sample: http://codepad.org/JqUspMPx

用法示例：http：//codepad.org/JqUspMPx

#3

try this

尝试这个

preg_replace('/^[a-zA-Z]\s/', 'ReplacementWord ', $string)

what it does is select anything from start till first white space and replace it with replcementWord . notice a space after replcementWord. this is because we added \s in search string

它的作用是从开始到第一个空格中选择任何东西并用replcementWord替换它。在replcementWord之后注意一个空格。这是因为我们在搜索字符串中添加了\ s

#4

preg_replace('/nothing/', 'something', $str, 1);

#5

-1

I ran to this issue and wanted a solution and this wasn't 100% right for me because if the string was like $str = "mine'this , the appostrophe would cause a problem. so I came up with a litle trick :

我遇到了这个问题，想要一个解决方案，这对我来说并不是100％正确，因为如果字符串就像$ str =“mine'this，那么appostrophe会引起问题。所以我想出了一个小问题：

$stick='';
$cook = explode($str,$cookie,2);
        foreach($cook as $c){
            if(preg_match("/^'/", $c)||preg_match('/^"/', $c)){
                //we have 's dsf fds... so we need to find the first |sess| because it is the delimiter'
                $stick = '|sess|'.explode('|sess|',$c,2)[1];
            }else{
                $stick = $c;
            }
            $cookies.=$stick;
        }

#6

-1

This checks and caches the first substring position in one command, next replacing it if present, should be the more compact and performant:

这将在一个命令中检查并缓存第一个子字符串位置，如果存在，则替换它，应该是更紧凑和高性能：

if(($offset=strpos($string,$replaced))!==false){
   $string=substr_replace($replaced,$replacer,$offset,strlen($replaced));
}

#7

-3

This function str_replace is the one you are looking for.

这个函数str_replace是你要找的那个。

#8

-3

ltrim() will remove the unwanted text at the beginning of a string.

ltrim（）将删除字符串开头的不需要的文本。

$do = 'nothing'; // what you want
$dont = 'something'; // what you dont want
$str = 'something inside';
$newstr = $do.ltrim( $str , $dont);
echo $newstr.'<br>';

#1