PHP Manual: vfprintf

Description

function vfprintf(resource $stream, string $format, array $values): int

Write a string produced according to format to the stream resource specified by stream.

Operates as fprintf() but accepts an array of arguments, rather than a variable number of arguments.

Parameters

stream

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 `+`. By default only negative numbers 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 value.
`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 coerced 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, an 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, an 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, an E_WARNING was emitted instead.

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

Changelog

Version	Description
8.5.0	A formatter that does not specify a precision now correctly treats it as a precision of `0`, instead of incorrectly resetting the precision.
8.0.0	This function no longer returns `false` on failure.
8.0.0	Throws a ValueError if the number of arguments is zero; previously this function emitted an `E_WARNING` instead.
8.0.0	Throws a ValueError if `[width]` is less than zero or bigger than `PHP_INT_MAX`; previously this function emitted an `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 an `E_WARNING` instead.
8.0.0	Throws a ValueError when fewer arguments are given than required; previously this function emitted an `E_WARNING` instead.

Examples

Example #1 vfprintf(): zero-padded integers

<?php
if (!($fp = fopen('date.txt', 'w')))
    return;

$year = 2025;
$month = 5;
$day = 6;
vfprintf($fp, "%04d-%02d-%02d", array($year, $month, $day));
// will write the formatted ISO date to date.txt
?>

vfprintf