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fprintf

Description

The fprintf of String for PHP write a formatted string to a stream.

Syntax

fprintf(
    resource $stream,
    string $format,
    mixed ...$values
): int

Parameters

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.

argnum

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

flags
FlagDescription
-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.
0Only 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.

specifier
SpecifierDescription
%A literal percent character. No argument is required.
bThe argument is treated as an integer and presented as a binary number.
cThe argument is treated as an integer and presented as the character with that ASCII.
dThe argument is treated as an integer and presented as a (signed) decimal number.
eThe argument is treated as scientific notation (e.g. 1.2e+2). The precision specifier stands for the number of digits after the decimal point.
ELike the e specifier but uses uppercase letter (e.g. 1.2E+2).
fThe argument is treated as a float and presented as a floating-point number (locale aware).
FThe argument is treated as a float and presented as a floating-point number (non-locale aware).
gGeneral 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.
GLike the g specifier but uses E and f.
oThe argument is treated as an integer and presented as an octal number.
sThe argument is treated and presented as a string.
uThe argument is treated as an integer and presented as an unsigned decimal number.
xThe argument is treated as an integer and presented as a hexadecimal number (with lowercase letters).
XThe 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:

TypeSpecifiers
strings
integerd, u, c, o, x, X, b
doubleg, G, e, E, f, F

values

Return

Returns the length of the string written.

Examples

1 · stream format values · single

<?

$filename = $_SERVER['DOCUMENT_ROOT'] . '/assets/txt/1.txt';
$mode = 'w+';

$stream = fopen($filename, $mode);

    $format = '%01.2f';
    $values = 1234.5;

    fprintf($stream, $format, $values);

    rewind($stream);

    $length = filesize($filename);

    $fread = fread($stream, $length);

    echo $fread;

fclose($stream);

1234.50

2 · stream format values · multiple

<?

$filename = $_SERVER['DOCUMENT_ROOT'] . '/assets/txt/1.txt';
$mode = 'w+';

$stream = fopen($filename, $mode);

    $format = '%04d-%02d-%02d';
    $values1 = date('Y');
    $values2 = date('m');
    $values3 = date('d');

    fprintf($stream, $format, $values1, $values2, $values3);

    rewind($stream);

    $length = filesize($filename);

    $fread = fread($stream, $length);

    echo $fread;

fclose($stream);

2026-04-27

3 · return

<?

$filename = $_SERVER['DOCUMENT_ROOT'] . '/assets/txt/1.txt';
$mode = 'w';

$stream = fopen($filename, $mode);

    $format = '%04d-%02d-%02d';
    $values1 = date('Y');
    $values2 = date('m');
    $values3 = date('d');

    $return = fprintf($stream, $format, $values1, $values2, $values3);

    echo $return;

fclose($stream);

10