php替换字符串中第N次出现的字符代码_PHP教程

/*
* $text是输入的文本；
* $word是原来的字符串；
* $cword是需要替换成为的字符串；
* $pos是指$word在$text中第N次出现的位置，从1开始算起
*
*/
function changeNstr($text,$word,$cword,$pos=1){
$text_array=explode($word,$text);
$num=count($text_array)-1;
if($pos>$num){
return "the number is too big!or can not find the $word";
}
$result_str='';
for($i=0;$i<=$num;$i++){
if($i==$pos-1){
$result_str.=$text_array[$i].$cword;
}else{
$result_str.=$text_array[$i].$word;
}
}
return rtrim($result_str,$word);
}
$text='hello world hello pig hello cat hello dog hello small boy';
$word='hello';
$cword='good-bye';
echo changeNstr($text,$word,$cword,3);
//输出：hello world hello pig good-bye cat hello dog hello small boy
?>

$regex = "/(,|，|||｜)/i";
$test = "河北，石家庄，北京,上海|天津｜｜｜重庆｜保定,,,河南， ";
$result = preg_replace($regex," ",$test);
print_r($result);
?>