$a = 'cdacdfigcd';
$count = strpos($a,"cd"); //strpos(string,find,start)返回所筛选的字符串出现的位置 参数start可选
$a = substr_replace($a,"",$count,2)//substr_replace(string,replacement,start,length)参数length可选
echo $a;输出acdfigcd
$a = 'cdacdfigcd';
$count = strpos($a,"cd"); //strpos(string,find,start)返回所筛选的字符串出现的位置 参数start可选
$a = substr_replace($a,"",$count,2)//substr_replace(string,replacement,start,length)参数length可选
echo $a;输出acdfigcd