Conversion Specifier for printf() and sprintf()

You have already been told about the Type specifiers for printf() and scanf(). Now here’s the complete list of conversion specifiers for printf() and scanf().

The format string in sprintf() and printf() 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.

Each conversion specification consists of a percent sign (%), followed by one or more of these elements, in order:

1. An optional sign specifier that forces a sign (- or +) to be used on a number. By default, only the - sign is used on a number if it's negative. This specifier forces positive numbers to have the + sign attached as well, and was added in PHP 4.3.0.
2. An optional padding specifier that says what character will be used for padding the results to the right string size. This may be a space character or a 0 (zero character). The default is to pad with spaces. An alternate padding character can be specified by prefixing it with a single quote (').
3. An optional alignment specifier that says if the result should be left-justified or right-justified. The default is right-justified; a (-) character here will make it left-justified.
4. An optional number, a width specifier that says how many characters (minimum) this conversion should result in.
5. An optional precision specifier in the form of a period (`.') followed by an optional decimal digit string that says how many decimal digits should be displayed for floating-point numbers. When using this specifier on a string, it acts as a cutoff point, setting a maximum character limit to the string.
6. n$position specifier is some interesting specifier in which n depicts the position of the variable in the declaration of a function.

For all these specifiers examples are provided below. Read them carefully.

The format string supports argument numbering/swapping. Here is an example:

<?php
$num = 5;
$location = 'tree';
$format = 'There are %d monkeys in the %s';
echo sprintf($format, $num, $location);
?>

Output:

There are 5 monkeys in the tree

<?php
$format = 'The %2$s contains %1$d monkeys';
echo sprintf($format, $num, $location);
?>

Output:

The tree contains 5 monkeys

Example for Type identifiers:

<?php
$n = 43951789;
$u = -43951789;
$c = 65; // ASCII 65 is 'A'
// notice the double %%, this prints a literal '%' character
printf("%%b = '%b'\n", $n); // binary representation
printf("%%c = '%c'\n", $c); // print the ascii character, same as chr() function
printf("%%d = '%d'\n", $n); // standard integer representation
printf("%%e = '%e'\n", $n); // scientific notation
printf("%%u = '%u'\n", $n); // unsigned integer representation of a positive integer
printf("%%u = '%u'\n", $u); // unsigned integer representation of a negative integer
printf("%%f = '%f'\n", $n); // floating point representation
printf("%%o = '%o'\n", $n); // octal representation
printf("%%s = '%s'\n", $n); // string representation
printf("%%x = '%x'\n", $n); // hexadecimal representation (lower-case)
printf("%%X = '%X'\n", $n); // hexadecimal representation (upper-case)
printf("%%+d = '%+d'\n", $n); // sign specifier on a positive integer
printf("%%+d = '%+d'\n", $u); // sign specifier on a negative integer
?>

Output:

%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'

Take another example for string specifier:

<?php
$s = 'monkey';
$t = 'many monkeys';
printf("[%s]\n", $s); // standard string output
printf("[%10s]\n", $s); // right-justification with spaces
printf("[%-10s]\n", $s); // left-justification with spaces
printf("[%010s]\n", $s); // zero-padding works on strings too
printf("[%'#10s]\n", $s); // use the custom padding character '#'
printf("[%10.10s]\n", $t); // left-justification but with a cutoff of 10 characters
?>

Output:

[monkey]
[    monkey]
[monkey    ]
[0000monkey]
[####monkey]
[many monke]

 

Note:-

•  A plus sign ('+') means put a '+' before positive numbers while a minus sign ('-') means left justify
• Padding with a '0' is different than padding with other characters. Zeros will only be added at the front of a number, after any sign. Other characters will be added before the sign, or after the number