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printf

(PHP 4, PHP 5, PHP 7)

printfOutput a formatted string

Description

printf ( string $format [, mixed $... ] ) : int

Produces output according to format.

Parameters

format

The format string is composed of zero or more directives: ordinary characters (excluding %) that are copied directly to the result and conversion specifications, each of which results in fetching its own parameter.

A conversion specification follows this prototype: %[flags][width][.precision]specifier.

Flags
Flag Description
- Left-justify within the given field width; Right justification is the default
+ Prefix positive numbers with a plus sign +; Default only negative are prefixed with a negative sign.
(space) Pads the result with spaces. This is the default.
0 Only left-pads numbers with zeros. With s specifiers this can also right-pad with zeros.
'(char) Pads the result with the character (char).

Width

An integer that says how many characters (minimum) this conversion should result in.

Precision

A period . followed by an integer who's meaning depends on the specifier:

  • For e, E, f and F specifiers: this is the number of digits to be printed after the decimal point (by default, this is 6).
  • For g and G specifiers: this is the maximum number of significant digits to be printed.
  • For s specifier: it acts as a cutoff point, setting a maximum character limit to the string.

Note: If the period is specified without an explicit value for precision, 0 is assumed.

Note: Attempting to use a position specifier greater than PHP_INT_MAX will generate warnings.

Specifiers
Specifier Description
% A literal percent character. No argument is required.
b The argument is treated as an integer and presented as a binary number.
c The argument is treated as an integer and presented as the character with that ASCII.
d The argument is treated as an integer and presented as a (signed) decimal number.
e The argument is treated as scientific notation (e.g. 1.2e+2). The precision specifier stands for the number of digits after the decimal point since PHP 5.2.1. In earlier versions, it was taken as number of significant digits (one less).
E Like the e specifier but uses uppercase letter (e.g. 1.2E+2).
f The argument is treated as a float and presented as a floating-point number (locale aware).
F The argument is treated as a float and presented as a floating-point number (non-locale aware). Available as of PHP 5.0.3.
g

General format.

Let P equal the precision if nonzero, 6 if the precision is omitted, or 1 if the precision is zero. Then, if a conversion with style E would have an exponent of X:

If P > X ≥ −4, the conversion is with style f and precision P − (X + 1). Otherwise, the conversion is with style e and precision P − 1.

G Like the g specifier but uses E and F.
o The argument is treated as an integer and presented as an octal number.
s The argument is treated and presented as a string.
u The argument is treated as an integer and presented as an unsigned decimal number.
x The argument is treated as an integer and presented as a hexadecimal number (with lowercase letters).
X The argument is treated as an integer and presented as a hexadecimal number (with uppercase letters).

Warning

The c type specifier ignores padding and width

Warning

Attempting to use a combination of the string and width specifiers with character sets that require more than one byte per character may result in unexpected results

Variables will be co-erced to a suitable type for the specifier:

Type Handling
Type Specifiers
string s
integer d, u, c, o, x, X, b
double g, G, e, E, f, F

...

Return Values

Returns the length of the outputted string.

Examples

Example #1 printf(): various examples

<?php
$n 
=  43951789;
$u = -43951789;
$c 65// ASCII 65 is 'A'

// notice the double %%, this prints a literal '%' character
printf("%%b = '%b'\n"$n); // binary representation
printf("%%c = '%c'\n"$c); // print the ascii character, same as chr() function
printf("%%d = '%d'\n"$n); // standard integer representation
printf("%%e = '%e'\n"$n); // scientific notation
printf("%%u = '%u'\n"$n); // unsigned integer representation of a positive integer
printf("%%u = '%u'\n"$u); // unsigned integer representation of a negative integer
printf("%%f = '%f'\n"$n); // floating point representation
printf("%%o = '%o'\n"$n); // octal representation
printf("%%s = '%s'\n"$n); // string representation
printf("%%x = '%x'\n"$n); // hexadecimal representation (lower-case)
printf("%%X = '%X'\n"$n); // hexadecimal representation (upper-case)

printf("%%+d = '%+d'\n"$n); // sign specifier on a positive integer
printf("%%+d = '%+d'\n"$u); // sign specifier on a negative integer
?>

The above example will output:

%b = '10100111101010011010101101'
%c = 'A'
%d = '43951789'
%e = '4.39518e+7'
%u = '43951789'
%u = '4251015507'
%f = '43951789.000000'
%o = '247523255'
%s = '43951789'
%x = '29ea6ad'
%X = '29EA6AD'
%+d = '+43951789'
%+d = '-43951789'

Example #2 printf(): string specifiers

<?php
$s 
'monkey';
$t 'many monkeys';

printf("[%s]\n",      $s); // standard string output
printf("[%10s]\n",    $s); // right-justification with spaces
printf("[%-10s]\n",   $s); // left-justification with spaces
printf("[%010s]\n",   $s); // zero-padding works on strings too
printf("[%'#10s]\n",  $s); // use the custom padding character '#'
printf("[%10.9s]\n"$t); // right-justification but with a cutoff of 8 characters
printf("[%-10.9s]\n"$t); // left-justification but with a cutoff of 8 characters
?>

The above example will output:

[monkey]
[    monkey]
[monkey    ]
[0000monkey]
[####monkey]
[ many monk]
[many monk ]

See Also

  • print - Output a string
  • sprintf() - Return a formatted string
  • fprintf() - Write a formatted string to a stream
  • vprintf() - Output a formatted string
  • vsprintf() - Return a formatted string
  • vfprintf() - Write a formatted string to a stream
  • sscanf() - Parses input from a string according to a format
  • fscanf() - Parses input from a file according to a format
  • number_format() - Format a number with grouped thousands
  • date() - Format a local time/date
  • flush() - Flush system output buffer

add a note add a note

User Contributed Notes 15 notes

up
6
dhosek at excite dot com
19 years ago
Be careful:
printf ("(9.95 * 100) = %d \n", (9.95 * 100));

'994'

First %d converts a float to an int by truncation.

Second floats are notorious for tiny little rounding errors.
up
3
php at mole dot gnubb dot net
14 years ago
[Editor's Note: Or just use vprintf...]

If you want to do something like <?php printf('There is a difference between %s and %s', array('good', 'evil')); ?> (this doesn't work)  instead of <?php printf('There is a difference between %s and %s', 'good', 'evil'); ?> you can use this function:

<?php
function printf_array($format, $arr)
{
    return
call_user_func_array('printf', array_merge((array)$format, $arr));
}
?>

Use it the following way:
<?php
$goodevil
= array('good', 'evil');
printf_array('There is a difference between %s and %s', $goodevil);
?>
and it will print:
There is a difference between good and evil
up
1
deekayen at hotmail dot com
17 years ago
You can use this function to format the decimal places in a number:

$num = 2.12;
printf("%.1f",$num);

prints:

2.1

see also: number_format()
up
0
maybird99 at yahoo dot com
17 years ago
instead of writing a function to round off a float (let's call it 'x') accurately, it's much easier to add a small number to x and then truncate it...
For example: if you want to round off to the nearest integer, just add 0.5 to x and then truncate it. if x=12.6, then it would calculate 13.1, and truncate it to 13. If x=14.4, it would calculate 14.9 and truncate it to 14.
up
-6
shepard at ameth dot org
17 years ago
Be sure that the output channel is available to write on before executing printf()!  Some functions in classes available from various sources (in my case, DB_Sql::query() in PHPLIB) assume that printing will work, even after the default output stream has been closed. 

For me the issue was most notable in PHP4 session management when I was creating my own sess_write() handler.  Since I was unable to find any function that checks for the output stream that printf() uses, I just had to drop the crazy use of the printf(). (does some function already exist to check for the presence of an output stream?)
up
-11
spiffytech at gmail dot com
7 years ago
Be careful when relying on typecasting with printf(). For example,

    printf("%d", "17,999")

returns "17".
up
-10
kalai_msc29 at rediffmail dot com
12 years ago
//If you want to make many Hidden fields you can use the function
//You can pass the values as array value,This will help you, when you are going to post many hiddend fields:-
function MakeHidden($ArrValues)
    {
       global $dearvar;
       echo $dearvar;
       if(is_array($ArrValues)){
             foreach($ArrValues as $key=>$values)
              {
                 echo $MakeHTML = "<input type='hidden' name='$values' value='$values'>";
               }
      }   
     
     
      else {
            echo $MakeHTML = "<input type='hidden' name='$ArrValues' value='$ArrValues'>";
         }
   return $MakeHTML;
}

//example:-

MakeHidden(array("value1","value2","value3"));

//OutPut :-

<input type="hidden" value="value1" name="value1"/>
<input type="hidden" value="value2" name="value2"/>
<input type="hidden" value="value3" name="value3"/>
up
-10
eugenew at starhub dot net dot sg
16 years ago
If anyone is looking for writing a quine using printf(),
this is my example:

<?php $f='<?php $f=%c%s%c; printf($f,39,$f,39); ?>'; printf($f,39,$f,39); ?>

This also helps those who are new to printf() see one way of using the 'mixed args' part, rather than just a single argument as in most examples I've seen.
up
-16
creating dot www at gmail dot com
4 years ago
Why rounding is not same as for round()?

Try this code:

<?php
printf
("%.02lf\n", 1.035);
printf("%.02lf\n", round(1.035, 2));
?>
Result:
1.03
1.04

In my opion it should be:
1.04
1.04

Why is that?
up
-13
dalu at uni SPAMHAM dot de
16 years ago
copypasted from msdn

A format specification, which consists of optional and required fields, has the following form:

%[flags] [width] [.precision] [{h | l | I64 | L}]type

Each field of the format specification is a single character or a number signifying a particular format option. The simplest format specification contains only the percent sign and a type character (for example, %s). If a percent sign is followed by a character that has no meaning as a format field, the character is copied to stdout. For example, to print a percent-sign character, use %%.

The optional fields, which appear before the type character, control other aspects of the formatting, as follows:

type
Required character that determines whether the associated argument is interpreted as a character, a string, or a number (see the printf Type Field Characters table.
flags
Optional character or characters that control justification of output and printing of signs, blanks, decimal points, and octal and hexadecimal prefixes (see the Flag Characters table). More than one flag can appear in a format specification.
width
Optional number that specifies the minimum number of characters output (see printf Width Specification).
precision
Optional number that specifies the maximum number of characters printed for all or part of the output field, or the minimum number of digits printed for integer values (see the How Precision Values Affect Type table).
h | l | I64 | L
Optional prefixes to type-that specify the size of argument (see the Size Prefixes for printf and wprintf Format-Type Specifiers table).
up
-11
RS
3 years ago
If your missing features such as "-"*100 to print a single character multiple times you can use the slightly longer and less readable PHP equivalent printf("%'-100s",""); and sprint("%'-100s","").
up
-15
ezislis at mail dot ru
17 years ago
be careful with integers, they cant hold large values.

printf("%d",10023123553.45634663);
will print out: 1433188961
and
printf("%.0f",10023123553.45634663);
will print out: 10023123553
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-18
sam[NOSPAM] at [NOSPAM]kingdomfaith dot com
17 years ago
I don't know if this is useful to anyone, but here goes! Example for using the printf function to output an object.

class person
{
    var $name = "";
    function name($newname = NULL)
    {
        if(! is_null($newname))
        {
            $this->name=$newname;
        }
        return $this->name;
    }
    var $surname = "";
    function surname($newsurname = NULL)
    {
        if(! is_null($newsurname))
        {
            $this->surname=$newsurname;
        }
        return $this->surname;
    }
    var $age = "";
    function age($newage = NULL)
    {
        if(! is_null($newage))
        {
            $this->age=$newage;
        }
        return $this->age;
    }
}

$bob = new person;
$bob->name('Bob');
$bob->surname('Builder');
$bob->age('50');

printf("Hi %s, your surname is %s and you are %s years old", $bob->name, $bob->surname, $bob->age);

Outputs:

Hi Bob, your surname is Builder and you are 50 years old
up
-19
codeslinger at compsalot dot com
14 years ago
Several people have commented about problems with aligning numbers.  I just wanted to add a bit of clarification.

According to the spec all True Type Fonts (especially porpotional spaced fonts) use a fixed width for numeric digits.  All digits have the same width which is equal to the width of "0".

Where things go haywire when trying to align numbers is that the space character does not have the same width as a digit when using a porportional spaced font.

Therefore if you want to line up a column of numbers, you can not use leading spaces to position them unless you use the same quantity of space characters for each row. e.g. your numbers have leading zeros etc.

The simplest solution is to switch to a monospaced font.  Alternativly you can use positioning tags.

Summary: Your numbers will always line up properly regardless of the font used, if you get the starting position to be consistant.
up
-24
lordfarquaad at notredomaine dot net
15 years ago
In response to chris dot breen at accurate dot com :

This will work, but i didn't try:
<?php
$format
= 'The %2$s contains %1$d monkeys.
         That is a nice %2$s full of %1$d monkeys.'
;
printf($format, $num, $location);
?>

Your problem came from the fact that in the string "\$s", the $ is simply escaped by the \, but but you must not do that with single quoted strings. Try to echo your strings to test it, or just go to http://www.php.net/manual/en/language.types.string.php
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