Printf and sprintf formatting in PHP - Step-by-Step Execution

Concept Flow - Printf and sprintf formatting

Start

↓

Prepare format string

↓

Provide values to format

↓

Call printf or sprintf

↓

printf: Output formatted string directly

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sprintf: Return formatted string

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End

The program prepares a format string and values, then calls printf or sprintf to format the string. printf prints it directly, sprintf returns it.

Execution Sample

PHP

<?php
$number = 42;
printf("Number: %d\n", $number);
$str = sprintf("Hex: %x", $number);
echo $str;
?>

This code prints a decimal number using printf and stores a hex string using sprintf, then prints it.

Execution Table

Step	Action	Format String	Value	Result/Output
1	Set $number	-	42	-
2	Call printf	Number: %d\n	42	Number: 42 (printed)
3	Call sprintf	Hex: %x	42	Hex: 2a (returned)
4	echo $str	-	-	Hex: 2a (printed)
5	End	-	-	Execution stops

💡 All statements executed, program ends.

Variable Tracker

Variable	Start	After Step 1	After Step 3	Final
$number	undefined	42	42	42
$str	undefined	undefined	Hex: 2a	Hex: 2a

Key Moments - 3 Insights

Why does printf print directly but sprintf does not?

printf outputs the formatted string immediately (see step 2 in execution_table), while sprintf returns the formatted string for later use (see step 3).

What does %d and %x mean in the format string?

%d formats the value as a decimal integer (step 2), %x formats it as a lowercase hexadecimal (step 3).

Why do we need to echo $str after sprintf?

sprintf returns the formatted string but does not print it, so echo is needed to display it (step 4).

Visual Quiz - 3 Questions

Look at the execution_table, what is printed by printf at step 2?

A 42

B Hex: 2a

C Number: 42

D Hex: 42

💡 Hint

Check the 'Result/Output' column at step 2 in execution_table.

At which step does $str get its value?

A Step 1

B Step 3

C Step 2

D Step 4

💡 Hint

Look at variable_tracker for $str changes and execution_table step 3.

If we change %x to %X in sprintf, what changes in output?

A Output becomes uppercase hex letters

B Output becomes decimal number

C Output becomes binary number

D No change in output

💡 Hint

Recall %x is lowercase hex, %X is uppercase hex formatting.

Concept Snapshot

printf and sprintf format strings with placeholders like %d, %x.
printf prints formatted string directly.
sprintf returns formatted string for later use.
Use echo to print sprintf result.
Placeholders control how values appear.

Full Transcript

This example shows how printf and sprintf work in PHP. First, a number 42 is stored in $number. Then printf prints 'Number: 42' using %d to format the number as decimal. Next, sprintf formats the number as hexadecimal with %x and returns the string 'Hex: 2a' which is stored in $str. Finally, echo prints the $str value. printf outputs immediately, sprintf returns a string. Placeholders like %d and %x control formatting style.