PHP: printf - Manual (original) (raw)

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

printf — Output a formatted string

Description

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 usesE and f.
h	Like the g specifier but uses F. Available as of PHP 8.0.0.
H	Like the g specifier but usesE 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](errorfunc.constants.php#constant.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](reserved.constants.php#constant.php-int-max). Prior to PHP 8.0.0, a [E_WARNING](errorfunc.constants.php#constant.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](reserved.constants.php#constant.php-int-max). Prior to PHP 8.0.0, a [E_WARNING](errorfunc.constants.php#constant.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](reserved.constants.php#constant.false) was returned and a [E_WARNING](errorfunc.constants.php#constant.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);//hexadecimalrepresentation(upper−case)printf("n); // hexadecimal representation (upper-case)printf("%%+d = '%+d'\n", n);//hexadecimalrepresentation(upper−case)printf("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'; <math xmlns="http://www.w3.org/1998/Math/MathML"><semantics><mrow><mi>t</mi><msup><mo>=</mo><mo mathvariant="normal" lspace="0em" rspace="0em">′</mo></msup><mi>m</mi><mi>a</mi><mi>n</mi><mi>y</mi><mi>m</mi><mi>o</mi><mi>n</mi><mi>k</mi><mi>e</mi><mi>y</mi><msup><mi>s</mi><mo mathvariant="normal" lspace="0em" rspace="0em">′</mo></msup><mo separator="true">;</mo><mi>p</mi><mi>r</mi><mi>i</mi><mi>n</mi><mi>t</mi><mi>f</mi><mo stretchy="false">(</mo><mi mathvariant="normal">"</mi><mo stretchy="false">[</mo></mrow><annotation encoding="application/x-tex">t = 'many monkeys';printf("[%s]\n", </annotation></semantics></math>t=′manymonkeys′;printf("[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 ]

Found A Problem?

dhosek at excite dot com ¶

26 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.

php at mole dot gnubb dot net ¶

20 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

deekayen at hotmail dot com ¶

24 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()

simon dot patrick at cantab dot net ¶

1 year 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.