PHP Snippets: Printf

This post is part of the PHP Snippets series where I will be covering the basics of developing in PHP.

The printf function is similar to the echo function in that it will output text, but differs in that it outputs a formatted string.

The syntax of the printf function is:

printf( string, arg 1, arg 2, ... )

Multiple arguments can be provided to the function for each of the placeholders to be replaced.

In the supplied string, placeholders prefixed with a % symbol are replaced with the parameters. Valid placeholders are:

Specifier	Description
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).

An example replacing a number and a string in a printf

$number = 500;
$string = 'miles';

printf( 'But I would walk %d %s', $number, $string );

If you have multiple argument and want to use some more than once, you can use argument numbering/swapping where the placeholder includes the argument number.

When using this numbering/swapping you add the argument number and a $ between the % and specifier. In the example below, there are three parameters where the numeric one is used twice:

$number = 500;
$string1 = 'miles';
$string2 = 'more';

printf( 'But I would walk %1$d %2$s<br />And I would walk %1$d %3$s', $number, $string1, $string2 );