strange behaviour on php

问题

Can some one please tell me why I get odd results rurning the following code?

<?php
class Bank
{
    var $ID;
    var $balance;
    var $name;
    function bank($name,$id,$balance=0)
    {
        $this->ID=$id;
        $this->balance=$balance;
        $this->name=$name;
    }
    function getBalance()
    {
        return $this->balance;
    }
    function setBalance($bal)
    {
        $this->balance=$bal;
    }
    function getId()
    {
        return $this->ID;
    }
    function setId($i)
    {
        $this->ID=$i;
    }
)
$b= new bank(yaniv,027447002, 15000);

Now when I try to echo:

$b->ID

Instead of the expected 027447002 I get an odd 6180354, but if I initiate the object like this :

$b=new bank(yaniv,'027447002',15000);

(notice I quoted the id property) it works OK. Any suggestion why is this happening and what is the right way to fix it?

回答1:

027447002 is in octal, as it prefixed with a zero. Convert that to decimal and you get 6180354!

See the manual page on integers for details.

回答2:

Remove the leading zero, because it makes PHP treat the number as an octal number.

回答3:

Because of the initial zero, it is interpreted as an octal number.

http://www.php.net/manual/en/language.types.integer.php

If the number should be left padded with zeros when printed (they are always a specific length) then you can use sprintf() to convert the stored integer to a zero padded string.

回答4:

Numeric literals with leading zeroes are how you specify something in octal (base 8). If you write 27447002 instead of 027447002 you'll be fine.

回答5:

Automatic base conversion. You don't even need all that class code to see this in action

echo 027447002;

The thing is that 027447002, in terms of numbers, is octal (base-8) - not a zero-filled decimal (base-10) integer.

回答6:

I have one comment besides what everyone else is saying.

It appears you want a 0 padded number, right? A nine digit number that's padded with zeros on the left?

Think about using str_pad function. Like so:

...
function bank($name, $id, $bal=0)
{
 ...
 $this->id = str_pad($id, 9, '0', STR_PAD_LEFT);
 ...
}
...

Then in your function you can call:

$b = new bank('John Doe', 12345678, 1.25);

If you output id, it would be padded

012345678

回答7:

As everyone rightly said - this is considered an octal value by default. I think the class constructor should be testing that it is a valid integer, and initiating the class should typecast the value...

function bank($name, $id, $balance=0)
{
    if (is_int($id))
      $this->ID=$id;
    else
      throw new Exception('ID is not integer');

    // and validate these too!
    $this->balance=$balance;
    $this->name=$name;
}

$b= new bank('yaniv', (int)027447002, 15000);

Hope that helps!

来源：https://stackoverflow.com/questions/1280039/strange-behaviour-on-php

标签

php

string

oop

octal