请教一个php正则的问题，字符串精确替换

[bluezsh]

比如这里字段值有 "111,222,111333,333,333333,"五个值
我想将 "333,"，替换为'' 最后结果为 "111,222,111333,333333,"三四个值，请问正则给如何写啊？

$str="333,";
$string = str_replace($str,'', "111,222,111333,333,333333,"); //这种方式不准确。

[xuzuning]

$str="/(?:^|,)333,/";
$string = preg_replace($str,',', "111,222,111333,333,333333,");

echo $string;

111,222,111333,333333,

[bluezsh]

非常感谢，但是我测试你这里有一个问题 $str="333,"; $string = preg_replace("/(?:^|,)$str/",',', "333,"); echo $string; 会输出一个','。

[misaka去年夏天]

<?php
$str=",333,";
$string = str_replace($str,',', "111,222,111333,333,333333,");
echo $string;

?>

[bluezsh]

引用 3 楼 misakaqunianxiatian 的回复:

<?php
$str=",333,";
$string = str_replace($str,',', "111,222,111333,333,333333,");
echo $string;

?>

我的现在就是前面没有“，”这个。

[李睿_Lee]

引用 4 楼 bluezsh 的回复:

[quote=引用 3 楼 misakaqunianxiatian 的回复:]

<?php
$str=",333,";
$string = str_replace($str,',', "111,222,111333,333,333333,");
echo $string;

?>

我的现在就是前面没有“，”这个。[/quote] 方法有很多的，前面没有逗号可以先加上，替换完了再去掉。我只是提一种思路，至于效率，另说了。