将1234567890转换成1,234,567,890 每3位用逗号隔开的形式

1.使用正则表达式解决！

    //将1234567890转换成1,234,567,890 每3位用逗号隔开的形式。  
    $str1 = "1234567890000";  
    preg_match("/^(/d{1,3})((/d{3})+)$/",$str1,$out);  
    echo "<pre>";  
    print_r($out);  
    echo "</pre>";  
    $new_str = preg_replace("/^(/d{1,3})((/d{3})+)$/","$1,$2",$str1);  
    print $new_str."/n";  
    $new_str = preg_replace("/(?<=/d{3})(/d{3})/",",$1",$new_str);  
    print $new_str."/n";  
    exit;  

$s = 77843229987422200;

echo number_format($s);

$s = "77843229987422200";  
$count = 4;  
echo $s;  
echo "<br>";  
echo test($s,$count);  
function test($s="",$count=3){  
    if(empty($s) || $count <= 0){  
        return false;  
    }  
    //反转  
    $str = strrev($s);  
    //分割  
    $arr = str_split($str,$count);  
    //连接  
    $new_s = join(",",$arr);  
    //再次反转  
    return strrev($new_s);  
      
} 

    function getString($str,$num,$sep)
    {
        $temp = strrev($str);
        $arr  = str_split($temp,$num);
        $length = count($arr);
        $temp = "";
        for($i=$length-1;$i>=0;$i--)
        {
            if($i>0)
                $temp=$temp.strrev($arr[$i]).$sep;
            else
                $temp=$temp.strrev($arr[$i]);
        }
        return $temp;
    }