PHP writes the formatted string to the specified output stream function vfprintf()

Example

Write some text to a text file named "test.txt":

<?php
$number = 9;
$str = "Beijing";
$file = fopen("test.txt","w");
echo vfprintf($file,"There are %u million bicycles in %s.",array($number,$str));
?>

The above code will output:

40

The following text Will be written to the file "test.txt":

There are 9 million bicycles in Beijing.

Definition and usage

vfprintf() function writes the formatted string to the specified output stream (Example: file or database).

Unlike fprintf(), the parameters in vfprintf() are located in an array. Array elements will be inserted into the main string at the percent sign (%). This function is executed step by step. At the first % sign, the first array element is inserted, at the second % sign, the second array element is inserted, and so on.

Note: If there are more % symbols than arg arguments, you must use placeholders. The placeholder is inserted after the % symbol and consists of a number and "\$". See Example 2.

Tip: Related functions: fprintf(), printf(), sprintf(), vprintf() and vsprintf()

Syntax

vfprintf(stream,format,argarray)

Required. An array with parameters to be inserted into the format string at % symbols.

Parameters

Description

stream

Required. Specifies where strings are written/output.

format

Required. Specifies a string and how to format variables within it.

Possible format values:

• %% - returns a percent sign %

• %b - a binary number

• %c - the character corresponding to the ASCII value

• %d - the decimal number containing the sign (negative, 0, positive)

• %e - Use lowercase scientific notation (e.g. 1.2e+2)

• ##%E - Use uppercase scientific notation (e.g. 1.2E+ 2)

• %u - Decimal number without sign (greater than or equal to 0)

• %f - Floating point number (local setting) )

• %F - floating point number (non-native setting)

##%g - shorter %e and %f
%G - shorter %E and %f

• ##%o - octal number

• %s - character String

• %x - Hexadecimal number (lowercase letters)

• ##%X - Hexadecimal number (uppercase letters)

• Additional format value. Must be placed between % and a letter (e.g. %.2f):

+ (Add + or - in front of a number to define the sign of the number. By default, only Negative numbers are marked, positive numbers are not marked)

• ' (Specifies what to use as padding, the default is spaces. It must be used with the width specifier. For example: %'x20s ( Use "x" as padding))

• - (Adjust the variable value left)

• [0-9] (Specify the minimum variable value Width)

• .[0-9] (Specifies the number of decimal places or the maximum string length)

• Note: If you use more than one of the above The format values ​​must be used in the order above and cannot be disrupted.

argarray

技术细节

返回值：	返回被写的字符串的长度。
PHP 版本：	5+

更多实例

实例 1

把一些文本写入到文件中：

<?php
$num1 = 123;
$num2 = 456;
$file = fopen("test.txt","w");
vfprintf($file,"%f%f",array($num1,$num2));
?>

下面的文本将被写入到文件 "test.txt"：

123.000000456.000000

实例 2

使用占位符：

<?php
$number = 123;
$file = fopen("test.txt","w");
vfprintf($file,"With 2 decimals: %1$.2f
nWith no decimals: %1$u",array($number));
?>

下面的文本将被写入到文件 "test.txt"：

With 2 decimals: 123.00
With no decimals: 123

实例 3

使用 printf() 来演示所有可能的格式值：

<?php
$num1 = 123456789;
$num2 = -123456789;
$char = 50; // The ASCII Character 50 is 2

// Note: The format value "%%" returns a percent sign
printf("%%b = %b <br>",$num1); // Binary number
printf("%%c = %c <br>",$char); // The ASCII Character
printf("%%d = %d <br>",$num1); // Signed decimal number
printf("%%d = %d <br>",$num2); // Signed decimal number
printf("%%e = %e <br>",$num1); // Scientific notation (lowercase)
printf("%%E = %E <br>",$num1); // Scientific notation (uppercase)
printf("%%u = %u <br>",$num1); // Unsigned decimal number (positive)
printf("%%u = %u <br>",$num2); // Unsigned decimal number (negative)
printf("%%f = %f <br>",$num1); // Floating-point number (local settings aware)
printf("%%F = %F <br>",$num1); // Floating-point number (not local settings aware)
printf("%%g = %g <br>",$num1); // Shorter of %e and %f
printf("%%G = %G <br>",$num1); // Shorter of %E and %f
printf("%%o = %o <br>",$num1); // Octal number
printf("%%s = %s <br>",$num1); // String
printf("%%x = %x <br>",$num1); // Hexadecimal number (lowercase)
printf("%%X = %X <br>",$num1); // Hexadecimal number (uppercase)
printf("%%+d = %+d <br>",$num1); // Sign specifier (positive)
printf("%%+d = %+d <br>",$num2); // Sign specifier (negative)
?>

vfprintf（格式化输出数据至文件）    

相关函数

   printf，fscanf，fprintf

表头文件

   #include<stdio.h>
#include<stdarg.h>

定义函数

int vfprintf(FILE *stream,const char * format,va_list ap);

函数说明

   vfprintf()会根据参数format字符串来转换并格式化数据，然后将结果输出到参数stream指定的文件中，直到出现字符串结束(’/0’)为止。关于参数format字符串的格式请参考printf()。va_list用法请参考附录C或vprintf()范例。
    返回值

   成功则返回实际输出的字符数，失败则返回-1，错误原因存于errno中。    

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