php string replacement problem

preg_replace function can match and replace according to a regular expression, and the number of times can be specified. Now I have a requirement like this. I want to replace the nth time of the specified match, such as a string. I wrote a regular expression, this The string can match a total of three places, and then I only want to replace the second match. What should I do? Is there such an implementation in php?

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preg_replace function can match and replace according to a regular expression, and the number of times can be specified. Now I have a requirement like this. I want to replace the nth time of the specified match, such as a string. I wrote a regular expression, this The string can match a total of three places, and then I only want to replace the second match. What should I do? Is there such an implementation in php?

Use preg_replace_callback
Please refer to the manual for usage

You can use preg_replace_callback to handle it. It calls other functions to handle replacement. You can handle the replacement logic yourself

Just go to the code:

<code>$i=1;
$result = preg_replace_callback('/a/',function($match)use(&$i){
    $match = $i != 2 ? $match[0] : '';
    $i++;
    return $match;
},'a1a2a3a4');
var_dump($result);</code>