，PHP替换指定位置的字符串

$a = '36,0.00,0.00,100<br><font color='#FF8000'>------解决思路----------------------</font><br>37,0.00,0.00,100<br><font color='#FF8000'>------解决思路----------------------</font><br>38,0.00,0.00,100<br><font color='#FF8000'>------解决思路----------------------</font><br>39,0.00,0.00,100';<br />$b='38';<br />$c='85';<br /><br />echo preg_replace_callback("/(^<br><font color='#FF8000'>------解决思路----------------------</font><br>\<br><font color='#FF8000'>------解决思路----------------------</font><br>$b,0.00,0.00,)100/", function($m) use ($c){ return $m[1].$c;}, $a);