PHP fprintf() Function
The PHP fprintf() function writes a string produced according to the specified format to the specified stream. If format includes format specifiers (sub-sequences beginning with %), the additional arguments following format are formatted and inserted in the resulting string replacing their respective specifiers.
After the format parameter, the function expects additional arguments at least as many as the number of format specifiers in the format string.
Syntax
fprintf(stream, format, arguments)
Parameters
stream |
Required. Specify the file pointer to write to. It must be valid, and must point to a file successfully typically opened by using fopen() function. | ||||||||||||||||||||||||||||||||||||
format |
Additional format values can be placed between the % and the specifier (e.g. %.3f). The possible values which can be placed in between are:
Note: If multiple additional format values are provided, they must be in %[flags][width][.precision]specifier order. | ||||||||||||||||||||||||||||||||||||
arguments |
Optional. Depending on the format string, a sequence of additional arguments should be passed in the function, each containing a value to replace a format specifiers in the format string. Number of arguments should be at least equal to the number of format specifiers in the format string. Additional arguments will be ignored by this function. |
Return Value
Returns the length of the string written.
Example: different specifiers
Lets assume that we have a file called test.txt in the current working directory. In the example below, this function is used to write the formatted string in this file.
<?php
//open the file in write mode
$fp = fopen("test.txt", "w+");
$n = 5000;
$u = -5000;
$c = 66; // ASCII 66 is 'B'
//%% is used to print '%' character
fprintf($fp, "%%b = %b\n", $n); //binary
fprintf($fp, "%%c = %c\n", $c); //ASCII character
fprintf($fp, "%%d = %d\n", $n); //integer
fprintf($fp, "%%e = %e\n", $n); //scientific notation
fprintf($fp, "%%u = %u\n", $n); //unsigned integer (+ve number)
fprintf($fp, "%%u = %u\n", $u); //unsigned integer (-ve number)
fprintf($fp, "%%f = %f\n", $n); //floating point
fprintf($fp, "%%o = %o\n", $n); //octal
fprintf($fp, "%%s = %s\n", $n); //string
fprintf($fp, "%%x = %x\n", $n); //hexadecimal (lowercase)
fprintf($fp, "%%X = %X\n", $n); //hexadecimal (uppercase)
fprintf($fp, "%%+d = %+d\n", $n); //sign specifier (+ve number)
fprintf($fp, "%%+d = %+d\n", $u); //sign specifier (-ve number)
//set the position to the start
rewind($fp);
//display the content of the file
while(!feof($fp)) {
echo fgets($fp);
}
//close the file
fclose ($fp);
?>
The output of the above code will be:
%b = 1001110001000 %c = B %d = 5000 %e = 5.000000e+3 %u = 5000 %u = 18446744073709546616 %f = 5000.000000 %o = 11610 %s = 5000 %x = 1388 %X = 1388 %+d = +5000 %+d = -5000
Example: using multiple % signs
In the example below, multiple % signs are used to place multiple additional arguments in the string written to the file.
<?php
//open the file in write mode
$fp = fopen("test.txt", "w+");
$name = 'John';
$age = 25;
fprintf($fp, "%s is %d years old.\n", $name, $age);
//using precision format
fprintf($fp, "%s is %.2f years old.\n", $name, $age);
//set the position to the start
rewind($fp);
//display the content of the file
while(!feof($fp)) {
echo fgets($fp);
}
//close the file
fclose ($fp);
?>
The output of the above code will be:
John is 25 years old. John is 25.00 years old.
Example: write a date string
In the example below, this function is used to write formatted date string in the file.
<?php
//open the file in write mode
$fp = fopen("test.txt", "w+");
$year = 2015;
$month = 5;
$day = 1;
//each format specifier specifies padding
//with 0 and width of the field
fprintf($fp, "Date is: %04d-%02d-%02d", $year, $month, $day);
//set the position to the start
rewind($fp);
//display the content of the file
while(!feof($fp)) {
echo fgets($fp);
}
//close the file
fclose ($fp);
?>
The output of the above code will be:
Date is: 2015-05-01
Example: string specifiers
Consider one more example to see how to use string specifiers with a given string.
<?php
//open the file in write mode
$fp = fopen("test.txt", "w+");
$x = 'catfish';
$y = 'many catfishes';
fprintf($fp, "[%s]\n", $x); //standard string output
fprintf($fp, "[%10s]\n", $x); //right-justification with spaces
fprintf($fp, "[%-10s]\n", $x); //left-justification with spaces
fprintf($fp, "[%010s]\n", $x); //zero-padding works on strings too
fprintf($fp, "[%'#10s]\n", $x); //using custom padding character '#'
fprintf($fp, "[%10.8s]\n", $y); //right-justification (8 characters cutoff)
fprintf($fp, "[%-10.8s]\n", $y); //left-justification (8 characters cutoff)
//set the position to the start
rewind($fp);
//display the content of the file
while(!feof($fp)) {
echo fgets($fp);
}
//close the file
fclose ($fp);
?>
The output of the above code will be:
[catfish] [ catfish] [catfish ] [000catfish] [###catfish] [ many cat] [many cat ]
❮ PHP String Reference
