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printf

(PHP 4, PHP 5, PHP 7, PHP 8)

printfOutput a formatted string

Description

printf(string $format, mixed ...$values): 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: %[argnum$][flags][width][.precision]specifier.

Argnum

An integer followed by a dollar sign $, to specify which number argument to treat in the conversion.

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

Either an integer that says how many characters (minimum) this conversion should result in, or *. If * is used, then the width is supplied as an additional integer value preceding the one formatted by the specifier.

Precision

A period . optionally followed by either an integer or *, whose 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, G, h and H 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. If * is used, the precision is supplied as an additional integer value preceding the one formatted by the specifier.

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).
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).
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.
h Like the g specifier but uses F. Available as of PHP 8.0.0.
H Like the g specifier but uses E and F. Available as of PHP 8.0.0.
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
int d, u, c, o, x, X, b
float e, E, f, F, g, G, h, H

values

Return Values

Returns the length of the outputted string.

Errors/Exceptions

As of PHP 8.0.0, a ValueError is thrown if the number of arguments is zero. Prior to PHP 8.0.0, a E_WARNING was emitted instead.

As of PHP 8.0.0, a ValueError is thrown if [width] is less than zero or bigger than PHP_INT_MAX. Prior to PHP 8.0.0, a E_WARNING was emitted instead.

As of PHP 8.0.0, a ValueError is thrown if [precision] is less than zero or bigger than PHP_INT_MAX. Prior to PHP 8.0.0, a E_WARNING was emitted instead.

As of PHP 8.0.0, a ArgumentCountError is thrown when less arguments are given than required. Prior to PHP 8.0.0, false was returned and a E_WARNING emitted instead.

Changelog

Version Description
8.0.0 This function no longer returns false on failure.
8.0.0 Throw a ValueError if the number of arguments is zero; previously this function emitted a E_WARNING instead.
8.0.0 Throw a ValueError if [width] is less than zero or bigger than PHP_INT_MAX; previously this function emitted a E_WARNING instead.
8.0.0 Throw a ValueError if [precision] is less than zero or bigger than PHP_INT_MAX; previously this function emitted a E_WARNING instead.
8.0.0 Throw a ArgumentCountError when less arguments are given than required; previously this function emitted a E_WARNING instead.

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("[%'#*s]\n", 10, $s); // Provide the padding width as an additional argument
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]
[####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 Unix timestamp
  • flush() - Flush system output buffer

add a note

User Contributed Notes 7 notes

up
20
dhosek at excite dot com
24 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
7
php at mole dot gnubb dot net
19 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
0
simon dot patrick at cantab dot net
3 months ago
A few things to note about printf:
1. The definition of specifier g (or G) is often wrongly stated as being "use e or f (or E or f), whichever results in the shorter string". The correct rule is given in the documentation and it does not always give this result.
2. For g/G/h/H, trailing zeros after the decimal point are removed (but not a zero just after the decimal point, in the e/E style).
3. g/G are locale-aware whether the e/E or f style is produced.
4. For b/o/x/X/u (that is, all integer styles except d) the result shown for negative values is the twos complement form of the number, 2**32 + v, where v is the (negative) value.
up
1
deekayen at hotmail dot com
23 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
-1
maybird99 at yahoo dot com
22 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
-1
Mario M. Junior
2 years ago
To provide a more user-friendly interface, you can use colors when printing text in the terminal.

p('Ordinary text.');
p('Warning: Check this out...', 'info');
p('Ops! Something went wrong.', 'error');
p('Yeah... done!', 'success');

function p($text, $style = '', $newLine = true) {

$styles = array(
'success' => "\033[0;32m%s\033[0m",
'error' => "\033[31;31m%s\033[0m",
'info' => "\033[33;33m%s\033[0m",

'Black' => "\033[0;30m%s\033[0m",
'Red' => "\033[0;31m%s\033[0m",
'Green' => "\033[0;32m%s\033[0m",
'Yellow' => "\033[0;33m%s\033[0m",
'Blue' => "\033[0;34m%s\033[0m",
'Purple' => "\033[0;35m%s\033[0m",
'Cyan' => "\033[0;36m%s\033[0m",
'Gray' => "\033[0;37m%s\033[0m",
'Graphite' => "\033[1;30m%s\033[0m",

'Bold Red' => "\033[1;31m%s\033[0m",
'Bold Green' => "\033[1;32m%s\033[0m",
'Bold Yellow' => "\033[1;33m%s\033[0m",
'Bold Blue' => "\033[1;34m%s\033[0m",
'Bold Purple' => "\033[1;35m%s\033[0m",
'Bold Cyan' => "\033[1;36m%s\033[0m",
'Bold White' => "\033[1;37m%s\033[0m",

'Bg Black' => "\033[40;1;37m%s\033[0m",
'Bg Red' => "\033[41;1;37m%s\033[0m",
'Bg Green' => "\033[42;1;37m%s\033[0m",
'Bg Yellow' => "\033[43;1;37m%s\033[0m",
'Bg Blue' => "\033[44;1;37m%s\033[0m",
'Bg Purple' => "\033[45;1;37m%s\033[0m",
'Bg Cyan' => "\033[46;1;37m%s\033[0m",
'Bg Gray' => "\033[47;1;37m%s\033[0m",

'Underscore' => "\033[4;37m%s\033[0m",
'Inverted' => "\033[7;37m%s\033[0m",
'Blink' => "\033[5;37m%s\033[0m",
);

$format = '%s';

if (isset($styles[$style])) {
$format = $styles[$style];
}

if ($newLine) {
$format .= PHP_EOL;
}

printf($format, $text);
}
up
-5
steve at myschoolsystems dot com
3 years ago
To format a dollar value as in $123.00 that may otherwise look like $123 use this

print ('$'); // the dollar sign in front of our answer
printf ('%.2f',$price);
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