(PHP 5, PHP 7, PHP 8)
fprintf — Write a formatted string to a stream
Write a string produced according to format
to the stream resource specified by stream
.
stream
A file system pointer resource that is typically created using fopen().
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
.
An integer followed by a dollar sign $
, to specify which number argument to treat in the conversion.
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). |
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.
A period .
optionally followed by either an integer or *
, whose meaning depends on the specifier:
e
, E
, f
and F
specifiers: this is the number of digits to be printed after the decimal point (by default, this is 6). g
, G
, h
and H
specifiers: this is the maximum number of significant digits to be printed. 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.
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). |
The c
type specifier ignores padding and width
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 | Specifiers |
---|---|
string | s |
int | d , u , c , o , x , X , b |
float | e , E , f , F , g , G , h , H |
values
Returns the length of the string written.
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.
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. |
Example #1 fprintf(): zero-padded integers
<?php
if (!($fp = fopen('date.txt', 'w'))) {
return;
}
fprintf($fp, "%04d-%02d-%02d", $year, $month, $day);
// will write the formatted ISO date to date.txt
?>
Example #2 fprintf(): formatting currency
<?php
if (!($fp = fopen('currency.txt', 'w'))) {
return;
}
$money1 = 68.75;
$money2 = 54.35;
$money = $money1 + $money2;
// echo $money will output "123.1";
$len = fprintf($fp, '%01.2f', $money);
// will write "123.10" to currency.txt
echo "wrote $len bytes to currency.txt";
// use the return value of fprintf to determine how many bytes we wrote
?>