PHP help understanding the number_format()

Posted on 2003-03-02
Medium Priority
Last Modified: 2008-03-03

I am just learning PHP and I can't understand why formating the same number twice gives a different result

I.E. the code below returns

Total including tax: $1,000.50
Total including tax: $1.00

Maybe someone could shed some light on this so I understand it better

$totalamount = 1000.50;
 $totalamount = number_format($totalamount, 2);
  echo "Total including tax: $".$totalamount."<br>\n";
  $totalamount = number_format($totalamount, 2);
    echo "Total including tax: $".$totalamount."<br>\n";

Question by:profess
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Expert Comment

ID: 8054077
If you check out the php manual:


you will see that the function number_format() has the following signature:

string number_format ( float number [, int decimals [, string dec_point [, string thousands_sep]]])

The function requires a floating-point number (float) as the first parameter, and you also supplied the number of decimal places (2) which is an integer (int) as the second parameter.

The function returns a String as its output.

The first time that you run execute the function, your code looks like this:

$totalamount = 1000.50;
$totalamount = number_format($totalamount, 2);

the second line is equivalent to:  $totalamount = number_format(1000.50, 2);

when this line is finished executing, you have changed $totalamount to a String $total amount is now equal to “1,000.50”

Now, the second time you execute the command, your code looks like this:

$totalamount = number_format($totalamount, 2);

This line is equivalent to writing:  $totalamount = number_format(“1,000.50”, 2);

Because the number_format function requires a float as the first parameter, and you supplied a string, php first converts your string to a float. Since the comma is a valid decimal separator in Europe, the floating-point number it converts to is 1.000.  So logically, your statement is equivalent to:  $totalamount = number_format(1.000, 2);

To solve the problem, don’t mix variable types, keep strings strings, and numbers numbers:

$fltTotalAmount = 1000.50;
$strTotalAmount = number_format($fltTotalAmount, 2);
 echo "Total including tax: $".$strTotalAmount."<br>\n";
 $strTotalAmount = number_format($fltTotalAmount, 2);
   echo "Total including tax: $".$strTotalAmount."<br>\n";


Accepted Solution

dboeke earned 200 total points
ID: 8054097
Because I copied and pasted, it changed my smart (or maybe they should be dumb) quotes to boxes like this:  ““““

The middle part of my answer should look like this:

When this line is finished executing, you have changed $totalamount to a String $total amount is now equal to "1,000.50"

Now, the second time you execute the command, your code looks like this:

$totalamount = number_format($totalamount, 2);

this line is equivalent to writing:  $totalamount = number_format("1,000.50", 2);

Author Comment

ID: 8054196
Thankyou, I had just accidently number_formated the same var twice the code was much larger and it was quite difficult to find....that is why I wanted to make sure I understood it.

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