在两个限制之间替换文本

I have been trying to get the text between two symbols to be replaced with preg_replace, but alas still not quite getting it right as I get a null output that is empty string, this is what I have so far

$start = '["';
$end   = '"]';
$msg   = preg_replace('#('.$start.')(.*)('.$end.')#si', '$1 test $3', $row['body']);

So an example output I am looking for would be:

normal text [everythingheregone] after text 

To

 normal text [test] after text

You are defining $start and $end as arrays, but using it as normal variables. Try changing your code to this:

$start = '\[';
$end  = '\]';
$msg = preg_replace('#('.$start.')(.*)('.$end.')#si', '$1 test $3', $row['body']);

$row['body']= "normal text [everythingheregone] after text ";
$start = '\[';
$end = '\]';
$msg = preg_replace('#'.$start.'.*?'.$end.'#s', '$1 [test] $3', $row['body']);
//output: normal text [test] after text done

How about

$str  = "normal text [everythingheregone] after text";
$repl = "test";
$patt = "/\[([^\]]+)\]/"; 
$res  = preg_replace($patt, "[". $repl ."]", $str);

Should yield normal text [test] after text

EDIT

Fiddle demo here

I have a regex approach. The regular expression is :\[.*?]

<?php
$string = 'normal text [everythingheregone] after text ';
$pattern = '\[.*?]';
$replacement = '[test]'
echo preg_replace($pattern, $replacement, $string);
//normal text [test] after text
?>

some functions that may help

function getBetweenStr($string, $start, $end)
    {
        $string = " ".$string;
        $ini = strpos($string,$start);
        if ($ini == 0) return "";
        $ini += strlen($start);    
        $len = strpos($string,$end,$ini) - $ini;
        return substr($string,$ini,$len);
    }

and

function getAllBetweenStr($string, $start, $end)
    {
        preg_match_all( '/' . preg_quote( $start, '/') . '(.*?)' . preg_quote( $end, '/') . '/', $string, $matches);
        return $matches[1];
    }