PHP 输出 pre_replace_callback

Question

我是php编码新手，我想输出第一个和第三个匹配项。下面的代码是我目前的编码。

$string="[nextpage] This is first text
[nextpage] This is the second text
[nextpage] This is the third text";
$string = preg_replace_callback("/\[nextpage\]([^\[nextpage\]]*)(.*?)(\n|\r\n?)/is", function ($submatch) {
    static $matchcount = 0;
    $matchcount++;
    $rtt=$submatch[2];
    return "<li>$rtt</li>";
  }, $string);
echo $string; //This is first text
                This is the second text
                This is the third text

我试过输出 $rtt=$submatch[0][1]; 以获得第一个匹配项，输出 $rtt=$submatch[0][3]; 以获得第三个匹配项，但不起作用。

预期结果；

//This is first text
  This is the third text

Answer 1

您没有使用 $matchcount 来测试它是哪个匹配项。

此外，匹配 \r 和 \n 不会匹配最后一行的结尾，因为它们之后没有换行符。您还需要匹配 $，这是字符串的结尾。

([^\[nextpage\]]*) 完全没有必要，并且不会像您认为的那样。 [^string] 并不意味着不匹配该字符串，它匹配任何不是这些字符之一的单个字符。

$string = preg_replace_callback("/\[nextpage\]([^\r\n]*)(\n|\r\n?|$)/is", function ($submatch) {
    static $matchcount = 0;
    $matchcount++;
    if ($matchcount == 1 || $matchcount == 3) {
        $rtt=$submatch[1];
        return "<li>$rtt</li>";
    } else {
        return "";
    }
  }, $string);

DEMO

Answer 2

也许需要采用不同的方法？

您可以将字符串拆分成一个数组，然后选择您关心的部分。

<?php
$string="[nextpage] This is first text
[nextpage] This is the second text
[nextpage] This is the third text";

$explosion = explode('[nextpage] ', $string);
var_dump($explosion);
$textICareAbout = trim($explosion[1]) . "  " . trim($explosion[3]);

echo $textICareAbout;

产量

array(4) {
  [0]=>
  string(0) ""
  [1]=>
  string(20) "This is first text
"
  [2]=>
  string(25) "This is the second text
"
  [3]=>
  string(22) "This is the third text"
}

This is first text  This is the third text

PHP 输出 pre_replace_callback

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