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HomeBackend DevelopmentPHP TutorialPHP only replaces the first occurrence of a string_PHP Tutorial
PHP only replaces the first occurrence of a string_PHP TutorialJul 13, 2016 pm 04:57 PM
phpgenerallyAppearexistcharacterstringusdesignationreplaceofwant

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 Copy code
 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 复制代码

function show_email_2($string){
        $first = strpos($string, '@');
        //var_dump($first);
        if($first==1){
            $string = '****'.$string;
        }
        if($first>1 && $first             $string = substr_replace($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 Copy code
function show_email_2($string){
           $first = strpos($string, '@');
​​​​ //var_dump($first);
           if($first==1){
               $string = '****'.$string;
         }
If($first>1 && $first               $string = substr_replace($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;$i if($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 复制代码

/*
 * $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;$i if($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
?>

Copy code

}

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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