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PHP fprintf() Function

PHP String Reference Complete PHP String Reference

Definition and Usage

The fprintf() function writes a formatted string to a specified output stream (example: file or database).

The arg1, arg2, ++ parameters will be inserted at percent (%) signs in the main string. This function works "step-by-step". At the first % sign, arg1 is inserted, at the second % sign, arg2 is inserted, etc.

The fprintf() function returns the length of the written string.

Syntax

fprintf(stream,format,arg1,arg2,arg++)

Parameter Description
stream Required. Specifies where to write/output the string
format Required. Specifies the string and how to format the variables in it.

Possible format values:

  • %% - Returns a percent sign
  • %b - Binary number
  • %c - The character according to the ASCII value
  • %d - Signed decimal number
  • %e - Scientific notation (e.g. 1.2e+2)
  • %u - Unsigned decimal number
  • %f - Floating-point number (local settings aware)
  • %F - Floating-point number (not local settings aware)
  • %o - Octal number
  • %s - String
  • %x - Hexadecimal number (lowercase letters)
  • %X - Hexadecimal number (uppercase letters)

Additional format values. These are placed between the % and the letter (example %.2f):

  • + (Forces both + and - in front of numbers. By default, only negative numbers are marked)
  • ' (Specifies what to use as padding. Default is space. Must be used together with the width specifier. Example: %'x20s (this uses "x" as padding)
  • - (Left-justifies the variable value)
  • [0-9] (Specifies the minimum width held of to the variable value)
  • .[0-9] (Specifies the number of decimal digits or maximum string length)

Note: If multiple additional format values are used, they must be in the same order as above.
arg1 Required. The argument to be inserted at the first %-sign in the format string
arg2 Optional. The argument to be inserted at the second %-sign in the format string
arg++ Optional. The argument to be inserted at the third, fourth, etc. %-sign in the format string

Tips and Notes

Note: If there are more % signs than arguments, you must use placeholders. A placeholder is inserted after the % sign, and consists of the argument- number and "\$". See example three.

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

Example 1

<?php
$str = "Hello";
$number = 123;
$file = fopen("test.txt","w");
echo fprintf($file,"%s world. Day number %u",$str,$number);
?>

The output of the code above will be:

27

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

Hello world. Day number 123

Example 2

<?php
$number = 123;
$file = fopen("test.txt","w");
fprintf($file,"%f",$number);
?>

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

123.000000

Example 3

Use of placeholders:

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

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

With 2 decimals: 123.00
With no decimals: 123

PHP String Reference Complete PHP String Reference
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