PHP only replaces the first occurrence of a string_PHP Tutorial

In PHP, when we want to replace specified characters in a string, we usually replace them all at once, such as the str_replace function, but sometimes we only want to replace the first occurrence, such as replacing keywords in an article. This cannot appear if there are 100 of them. 100 times, I just want to limit it a few times. Let me introduce to you how to achieve it.

Example

$str='This is a string. I only replace ABC once and I don’t replace the following ABC. Is there any way to achieve this? ';

Replace the first abc with xyz. Since the string to be replaced is fixed, many people think of using the str_replace() function to see if the use of this function is what we want

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

I accidentally thought that was what we wanted. The last parameter is to return the total number of replacements. It is a reference variable, not what I want to specify how many times it will be replaced, so use str_replace( ) is not possible

preg_replace() can be implemented, but it’s a pity that regular expressions are used,

The code is as follows

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代码如下	复制代码
$str=preg_replace('/abc/','abc',$str,1); echo $str;

$str=preg_replace('/abc/','abc',$str,1);
echo $str;

Example

Display email as starting from the first 2 digits of @ (inclusive) and hiding 4 digits forward

代码如下

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function show_email_2($string){         $first = strpos($string, '@');         //var_dump($first);         if($first==1){             $string = '****'.$string;         }         if($first>1 && $first<=5){ $string = substr_replace($string,'****',0,$first-1); } if($first>5){             $string = substr_replace($string,'****',$first-5,4);         }                 var_dump($string);         return $string;     }     //show_email_2('22@163.com');        //输出-->****2@163.com     //show_email_2('22@22.com');        //输出-->****2@22.com     show_email_2('6123456@163.com');    //输出-->61****6@163.com 有没有不用正则的，嗯可以这样 $replace='xyz'; if(($position=strpos($str,$replace))!==false){      $leng=strlen($replace);     $str=substr_replace($str,'abc',$position,$leng); } echo $str;

The code is as follows

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function show_email_2($string){            $first = strpos($string, '@'); ​​​​ //var_dump($first);            if($first==1){                $string = '****'.$string;          } If($first>1 && $first<=5){               $string = substr_replace($string,'****',0,$first-1);                                                                         }             if($first>5){                $string = substr_replace($string,'****',$first-5,4);          }                                                                                         var_dump($string);           return $string; } //show_email_2('22@163.com'); //Output-->****2@163.com //show_email_2('22@22.com'); //Output-->****2@22.com Show_email_2('6123456@163.com'); //Output-->61****6@163.com Is there any way to use regular expressions? Yes, it can be like this $replace='xyz'; if(($position=strpos($str,$replace))!==false){ $leng=strlen($replace); $str=substr_replace($str,'abc',$position,$leng); } echo $str;

If I want to replace to a specified number of times, please refer to the following method

/*
* $text is the input text;
* $word is the original string;
* $cword is the string that needs to be replaced;
* $pos refers to the position where $word appears for the Nth time in $text, counting from 1
* */
function changeNstr($text,$word,$cword,$pos=1){
$text_array=explode($word,$text);
$num=count($text_array)-1;
if($pos>$num){
return "the number is too big!or can not find the $word";
}
$result_str='';
for($i=0;$i<=$num;$i++){
if($i==$pos-1){
$result_str.=$text_array[$i].$cword;
}else{
$result_str.=$text_array[$i].$word;}

The code is as follows

代码如下

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/* * $text是输入的文本； * $word是原来的字符串； * $cword是需要替换成为的字符串； * $pos是指$word在$text中第N次出现的位置，从1开始算起 * */ function changeNstr($text,$word,$cword,$pos=1){ $text_array=explode($word,$text); $num=count($text_array)-1; if($pos>$num){ return "the number is too big!or can not find the $word"; } $result_str=''; for($i=0;$i<=$num;$i++){ if($i==$pos-1){ $result_str.=$text_array[$i].$cword; }else{ $result_str.=$text_array[$i].$word;} } return rtrim($result_str,$word); } $text='hello world hello pig hello cat hello dog hello small boy'; $word='hello'; $cword='good-bye'; echo changeNstr($text,$word,$cword,3); //输出：hello world hello pig good-bye cat hello dog hello small boy ?>

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}

return rtrim($result_str,$word);
}
$text='hello world hello pig hello cat hello dog hello small boy';
$word='hello';
$cword='good-bye';
echo changeNstr($text,$word,$cword,3);
//Output: hello world hello pig good-bye cat hello dog hello small boy
?>

The examples are easy to understand. If you don’t want to know more about it, we can just use str_replace. http://www.bkjia.com/PHPjc/631531.html

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http: //www.bkjia.com/PHPjc/631531.htmlTechArticleTo replace specified characters in a string in php, we usually replace them all at once, such as the str_replace function, but sometimes we just want Replace the first occurrence, like replacing the keywords of the article. If there is...