printf

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

printf — Muestra una string formateada

Descripción

printf(string $format, mixed ...$values): int

Muestra una string formateada.

Parámetros

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	Descripción
`-`	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.

Nota: 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	Descripción
`%`	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).

Advertencia

The c type specifier ignores padding and width.

Advertencia

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

Valores devueltos

Devuelve la longitud de la string mostrada.

Errores/Excepciones

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.

Historial de cambios

Versión	Descripción
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.

Ejemplos

Ejemplo #1 printf(): varios ejemplos

<?php
$n =  43951789;
$u = -43951789;
$c = 65; // ASCII 65 es 'A'

// note el doble %%, esto muestra un carácter '%' literal
printf("%%b = '%b'\n", $n); // representación binaria
printf("%%c = '%c'\n", $c); // muestra el carácter ascii, como la función chr()
printf("%%d = '%d'\n", $n); // representación estándar de un integer
printf("%%e = '%e'\n", $n); // notación científica
printf("%%u = '%u'\n", $n); // representación de integer sin signo de un integer positivo
printf("%%u = '%u'\n", $u); // representación de integer sin signo de un integer negativo
printf("%%f = '%f'\n", $n); // representación en coma flotante
printf("%%o = '%o'\n", $n); // representación octal
printf("%%s = '%s'\n", $n); // representación string
printf("%%x = '%x'\n", $n); // representación hexadecimal (minúscula)
printf("%%X = '%X'\n", $n); // representación hexadecimal (mayúscula)

printf("%%+d = '%+d'\n", $n); // indicación del signo para un integer positivo
printf("%%+d = '%+d'\n", $u); // indicación del signo para un integer negativo
?>

El resultado del ejemplo sería:

%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'

Ejemplo #2 printf(): especificadores de strings

<?php
$s = 'monkey';
$t = 'many monkeys';

printf("[%s]\n",        $s); // muestra de una string estándar
printf("[%10s]\n",      $s); // alineación a la derecha con espacios
printf("[%-10s]\n",     $s); // alineación a la izquierda con espacios
printf("[%010s]\n",     $s); // el espaciado nulo funciona también en strings
printf("[%'#10s]\n",    $s); // uso del carácter personalizado de separación '#'
printf("[%'#*s]\n", 10, $s); // Proporcionar el ancho de alineación como argumento adicional
printf("[%10.9s]\n",    $t); // alineación a la derecha pero con corte a 8 caracteres
printf("[%-10.9s]\n",   $t); // alineación a la izquierda pero con corte a 8 caracteres
?>

El resultado del ejemplo sería:

[monkey]
[    monkey]
[monkey    ]
[0000monkey]
[####monkey]
[####monkey]
[ many monk]
[many monk ]

Ver también

print - Muestra un string
sprintf() - Devuelve una string formateada
fprintf() - Escribe una cadena formateada en un flujo
vprintf() - Muestra una string formateada
vsprintf() - Devuelve una string formateada
vfprintf() - Escribe una cadena formateada en un flujo
sscanf() - Analiza una cadena utilizando un formato
fscanf() - Analiza un archivo según un formato
number_format() - Formatea un número para su visualización
date() - Da formato a una marca de tiempo de Unix (Unix timestamp)
flush() - Vacía los búferes de salida del sistema

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User Contributed Notes 4 notes

down

dhosek at excite dot com ¶

25 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.

down

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

down

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()

down

-1

simon dot patrick at cantab dot net ¶

10 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.

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