在线等，急。PHP替换指定位置的字符串

$a = '36,0.00,0.00,100|37,0.00,0.00,100|38,0.00,0.00,100|39,0.00,0.00,100';
$b='38';
$c='85';

用PHP怎么做一替换。。。 

就是说 当$a中 包含$b中的字数后。 把38，0.00，0.00，100 中的100替换成$c中的数字。

如果$b=‘37’

那么就把37，0.00，0.00，100 中的100替换成$c中的数字。


谢谢各位了

回复讨论(解决方案)

php5.3+ 通过

$a = '36,0.00,0.00,100|37,0.00,0.00,100|38,0.00,0.00,100|39,0.00,0.00,100';$b='38';$c='85';echo preg_replace_callback("/(^|\|$b,0.00,0.00,)100/", function($m) use ($c){ return $m[1].$c;}, $a);

php5.5- 还可写作

echo preg_replace("/(^|\|$b,0.00,0.00,)100/e", "'$1'.'$c'", $a);

用新的子字符串替换原始字符串中被指定要替换的字符串
<?php
$str2="某某";
$str1="**";
$str=" 某某公司是一家以计算机软件技术为核心的高科技企业，多年来始终致力于行业管理软件开发、数字化出版物制作、计算机网络系统综合应用以及行业电子商务网站开发等领域，涉及生产、管理、控制、仓贮、物流、营销、服务等行业";
echo str_ireplace($str2,$str1,$str);
?>

php5.3+ 通过

$a = '36,0.00,0.00,100|37,0.00,0.00,100|38,0.00,0.00,100|39,0.00,0.00,100';$b='38';$c='85';echo preg_replace_callback("/(^|\|$b,0.00,0.00,)100/", function($m) use ($c){ return $m[1].$c;}, $a);

#2 不就是吗？

#2 不就是吗？

不固定？
那你描述的不是固定的吗？

不固定？
那你描述的不是固定的吗？

$a = '36,0.00,0.00,100|37,0.00,0.00,100|38,0.01,0.00,100|39,0.00,0.00,100';$b='38';$c='85';echo "{$a}
";echo preg_replace_callback("/(^|\|$b,0.00,0.00,)100/", function($m) use ($c){ return $m[1].$c;}, $a).'
';echo preg_replace_callback("/(^|\|$b,\d\.\d{1,2},\d\.\d{1,2},)100/", function($m) use ($c){ return $m[1].$c;}, $a);

好吧，。，。是我错了。。。。我没有表答清楚。我开始以为很简单。结果我自已试了一下发现还不行

实际我要的效果是这样的

$a = '36,0.00,0.00,100|37,0.00,0.00,100|38,0.00,0.00,100|39,0.00,0.00,100';
$b='38';
$c='85';

就是说 当$a中 包含$b中的字数后。 把38，0.00，0.00，100 中的100取出来 然后用这个100 减去$c里面的数字。
最后等于这样 36,0.00,0.00,100|37,0.00,0.00,100| 38,0.00,0.00,15|39,0.00,0.00,100

然后入库、。。。。。。。其它我想要这个。。。把问题想简单了

求各位帮个忙吧

$a = '36,0.00,0.00,100|37,0.00,0.00,100|38,0.00,0.00,100|39,0.00,0.00,100';$b='38';$c='85'; echo preg_replace_callback("/(^|\|$b,0.00,0.00,)(100)/", function($m) use ($c){ return $m[1].($m[2]-$c);}, $a);

$a = '36,0.00,0.00,100|37,0.00,0.00,100|38,0.00,0.00,100|39,0.00,0.00,100';$b='38';$c='85'; echo preg_replace("/(^|\|$b,0.00,0.00,)(100)/e", "'$1'.($2-$c)", $a);

$a = '36,0.00,0.00,100|37,0.00,0.00,100|38,0.00,0.00,100|39,0.00,0.00,100';$b='38';$c='85'; echo preg_replace("/((?:^|\|$b),(?:[\d.]+,){2})(\d+)/e", "'$1'.($2-$c)", $a);

$a = '36,0.00,0.00,100|37,0.00,0.00,100|38,0.00,0.00,100|39,0.00,0.00,100';$b='38';$c='85'; echo preg_replace_callback("/(^|\|$b,0.00,0.00,)(100)/", function($m) use ($c){ return $m[1].($m[2]-$c);}, $a);

$a = '36,0.00,0.00,100|37,0.00,0.00,100|38,0.00,0.00,100|39,0.00,0.00,100';$b='38';$c='85'; echo preg_replace("/(^|\|$b,0.00,0.00,)(100)/e", "'$1'.($2-$c)", $a);

$a = '36,0.00,0.00,100|37,0.00,0.00,100|38,0.00,0.00,100|39,0.00,0.00,100';$b='38';$c='85'; echo preg_replace("/((?:^|\|$b),(?:[\d.]+,){2})(\d+)/e", "'$1'.($2-$c)", $a);