Incrementing a number with str_pad (PHP) [closed]

问题

I am creating an incrementing number starting with 1001. If the number goes 1001,1002,1003... when it reaches 10, will it be formatted like 1010 or will it be 10010? I need it to just go in order and be 1010 and when it reaches 100, 1100.

$prefix = "1"; // update the prefix here

    $number = 1;
    $number++;
    $unique = str_pad($number, 3, "0", STR_PAD_LEFT);
    $unique = $prefix . $unique;

print_r($unique);

回答1:

When your count reaches 10, the number printed will be 1010. As described here, str_pad "Pads a string to a certain length with another string" You can create a test with the following:

$prefix = "1"; // update the prefix here

$number = 1;

for ($number = 1; $number <= 100; $number++)
{    
  $unique = str_pad($number, 3, "0", STR_PAD_LEFT);
  $unique = $prefix . $unique;    
  print($unique."\n");
 }

When your count reaches 100, the number printed will be 1100.

However, if you were to go up to 1000, 11000 would be printed - str_pad apparently will not truncate the string to match the specified size.

回答2:

It will be 1010, but you can test this yourself easily:

$prefix = "1"; // update the prefix here

$number = 9;
$number++;
$unique = str_pad($number, 3, "0", STR_PAD_LEFT);
$unique = $prefix . $unique;

print_r($unique);  // 1010

The second argument of str_pad specifies padding. If padding is 3, then 1 becomes 001, 10 becomes 010, 100 becomes 100.

回答3:

With your code it will be 10010.

It looks like you are making this more complicated than it needs to be. Why not just start with $number = 1001 and increment it and then turn it into a string?

$number = 1001;
$number++;

$unique = strval($number);

print_r($unique);

来源：https://stackoverflow.com/questions/24809811/incrementing-a-number-with-str-pad-php

标签

php

string

increment