echo, print and printf

echo

echo is the everyday way to send output. In a command-line script the output goes to the terminal; in a web page it becomes part of the HTML. echo accepts several values separated by commas:

<?php
$name = "Liam";
echo "Hello, ", $name, "!\n";
echo "Hello, " . $name . "!\n";

Hello, Liam!
Hello, Liam!

Both lines print the same thing. The comma form passes several values to echo; the dot form builds one string first. Either is fine.

echo is a language construct rather than a function, so brackets are optional and usually left out. In templates you will often see the short form <?= $name ?>, which means <?php echo $name; ?>; the Mixing PHP and HTML lesson uses it.

print

print is almost the same, with two differences: it takes exactly one value, and it returns 1, so it can be used inside an expression. In practice almost everyone uses echo.

<?php
print "Printed with print\n";
$result = print "";
var_dump($result);

Printed with print
int(1)

printf: formatted output

Joining numbers and text with dots gets messy when you need a fixed number of decimals or aligned columns. printf() takes a format string with placeholders, then the values to put in them:

<?php
$product = "Mechanical Keyboard";
$price = 89.5;
$quantity = 2;

printf("%s x %d = %.2f\n", $product, $quantity, $price * $quantity);

Mechanical Keyboard x 2 = 179.00

Each placeholder starts with % and ends with a letter that says how to show the value:

<?php
printf("%d%% off\n", 15);
printf("%f\n", 2.5);
printf("%.1f\n", 2.46);
printf("%x\n", 255);
printf("%d\n", 9.99);

15% off
2.500000
2.5
ff
9

%.1f rounds (2.46 becomes 2.5), while %d cuts off the decimals (9.99 becomes 9), just like an (int) cast.

Width, padding and alignment

A number between % and the letter sets a minimum width. Text is right-aligned by default; a minus sign left-aligns it; a zero pads numbers with zeros:

<?php
printf("[%8s]\n", "mug");
printf("[%-8s]\n", "mug");
printf("[%05d]\n", 42);
printf("[%8.2f]\n", 3.14159);
printf("Order #%06d\n", 1042);

[     mug]
[mug     ]
[00042]
[    3.14]
Order #001042

That makes simple text reports easy to line up:

<?php
$items = [
    ["Mechanical Keyboard", 1, 89.5],
    ["Ceramic Mug Set", 4, 18.75],
    ["Water Bottle", 2, 12],
];

foreach ($items as [$name, $qty, $price]) {
    printf("%-20s %3d %9.2f\n", $name, $qty, $qty * $price);
}

Mechanical Keyboard    1     89.50
Ceramic Mug Set        4     75.00
Water Bottle           2     24.00

sprintf: format without printing

sprintf() takes the same arguments as printf() but returns the string instead of printing it. Use it when you need the formatted value in a variable, a message or a database:

<?php
$invoice = sprintf("INV-%04d-%s", 7, "2026");
$label = sprintf("%.1f%% complete", 66.666);

echo $invoice . "\n";
echo $label . "\n";

INV-0007-2026
66.7% complete

Arguments can also be numbered, %1$s, so one value can be used twice or the order can change, which is useful for translated messages: sprintf('%2$s, %1$s', 'Asha', 'Verma') gives Verma, Asha.

Debugging output

Arrays and objects cannot be printed with echo. Three functions show them while you are developing:

<?php
$product = ["name" => "Yoga Mat", "price" => 24.99, "tags" => ["fitness"]];

print_r($product);
var_export($product);
echo "\n";

Array
(
    [name] => Yoga Mat
    [price] => 24.99
    [tags] => Array
        (
            [0] => fitness
        )

)
array (
  'name' => 'Yoga Mat',
  'price' => 24.99,
  'tags' =>
  array (
    0 => 'fitness',
  ),
)

print_r() is the most readable. var_dump() (from Data types and var_dump) adds types and string lengths, which is what you want when a value is mysteriously wrong. var_export() prints valid PHP code you could paste back into a file. In a browser, wrap debugging output in <pre> tags so the line breaks show. Remove it all before the code goes live.

Common mistakes

• Trying to echo an array, which prints the word Array and a warning. Use print_r() or implode().
• Mixing up printf and sprintf: $text = printf(...) prints immediately and stores the length.
• Forgetting %% for a percent sign in a format string.
• Using printf to show money without rounding rules in mind. %.2f rounds half away from zero, like round().

Exercise

Print a receipt line for each item below, with the name left-aligned in 18 characters, the quantity right-aligned in 3, and the line total with 2 decimals in 8. Then print the grand total in the same column. Items: Puzzle 1000 Pieces, 1 at 19.99; Resistance Bands, 3 at 14.99.

<?php
$items = [["Puzzle 1000 Pieces", 1, 19.99], ["Resistance Bands", 3, 14.99]];
$total = 0;

foreach ($items as [$name, $qty, $price]) {
    $line = $qty * $price;
    $total += $line;
    printf("%-18s %3d %8.2f\n", $name, $qty, $line);
}
printf("%-22s %8.2f\n", "Total", $total);

Puzzle 1000 Pieces   1    19.99
Resistance Bands     3    44.97
Total                     64.96