# # Variadic Functions

What Is a Variadic Function?

In simple terms: A variadic function accepts any number of arguments. Instead of declaring a fixed list of parameters, you declare one parameter that collects all remaining arguments into an array.

Technically: A parameter prefixed with ... (the splat or spread operator) is a variadic parameter. When the function is called, all remaining positional arguments are collected into an array and assigned to that parameter.

function sum(int ...$numbers): int   // $numbers is an array of all passed integers

Why Variadic Functions Exist

Some operations naturally work on "one or more" or "zero or more" values: adding numbers, joining words, logging a message with any number of details, or finding the maximum. PHP's own max(), min(), printf(), and array_merge() work this way. Variadic parameters let your functions do the same.

---

Syntax

function functionName(Type $required, Type ...$rest)
{
    // $rest is an array of the remaining arguments
}

Example

<?php
function sum(int ...$numbers): int
{
    $total = 0;

    foreach ($numbers as $number) {
        $total += $number;
    }

    return $total;
}

echo sum(1, 2, 3) . "\n";
echo sum(10, 20, 30, 40, 50) . "\n";
echo sum() . "\n";

Output

6
150
0

How It Works

• ...$numbers collects all arguments into an array: sum(1, 2, 3) gives $numbers = [1, 2, 3].
• Calling sum() with no arguments gives an empty array, so the loop does not run and the result is 0.
• The type int applies to each collected argument. Passing a non-integer value that cannot be converted causes a TypeError.

(The body could simply be return array_sum($numbers); — the loop is shown to make the collected array visible.)

---

Combining Regular and Variadic Parameters

Regular parameters come first; the variadic parameter must be last, and there can be only one.

<?php
function joinWords(string $separator, string ...$words): string
{
    return implode($separator, $words);
}

echo joinWords(', ', 'PHP', 'MySQL', 'Laravel') . "\n";
echo joinWords(' | ', 'Home', 'Courses') . "\n";

Output

PHP, MySQL, Laravel
Home | Courses

The first argument always goes to $separator; every argument after it goes into $words.

Requiring at Least One Value

A variadic parameter accepts zero arguments. To require at least one, declare the first value as a normal parameter:

<?php
function maxOf(int $first, int ...$others): int
{
    return max($first, ...$others);
}

echo maxOf(3, 9, 4) . "\n";
echo maxOf(7) . "\n";

Output

9
7

Calling maxOf() with no arguments now throws an ArgumentCountError, which is correct — the maximum of nothing is undefined. Inside the function, ...$others unpacks the array again for max() (explained below).

---

Argument Unpacking: ... in Function Calls

The same ... operator works in the opposite direction in a call: it spreads an array (or other iterable) into separate arguments.

<?php
function sum(int ...$numbers): int
{
    return array_sum($numbers);
}

$cartPrices = [499, 1299];
$extraCharges = [100];

echo sum(...$cartPrices) . "\n";
echo sum(...$cartPrices, ...$extraCharges) . "\n";
echo sum(5, ...$cartPrices) . "\n";

$dateParts = [2026, 10, 15];
$date = new DateTimeImmutable();
echo $date->setDate(...$dateParts)->format('Y-m-d') . "\n";

Output

1798
1898
1803
2026-10-15

How It Works

• sum(...$cartPrices) is equivalent to sum(499, 1299).
• Several arrays can be unpacked in one call, and normal arguments can come before an unpacked array.
• Unpacking works with any function, not only variadic ones: setDate(...[2026, 10, 15]) passes three separate arguments to setDate($year, $month, $day).

Rule: In a call, a normal positional argument cannot come after an unpacked array. sum(...$cartPrices, 5) is a compile-time error ("Cannot use positional argument after argument unpacking"). Put the extra value first, or unpack [5] as another array.

Unpacking Arrays With String Keys (PHP 8.1+)

When an unpacked array has string keys, they are treated as named arguments:

<?php
function createUser(string $name, string $role = 'viewer'): string
{
    return "$name ($role)";
}

$data = ['name' => 'Asha', 'role' => 'admin'];
echo createUser(...$data) . "\n";

Output

Asha (admin)

---

Variadics and Named Arguments

A variadic parameter also collects named arguments that do not match a declared parameter, using the names as string keys:

<?php
function buildQuery(string $path, string|int ...$params): string
{
    return $params === [] ? $path : $path . '?' . http_build_query($params);
}

echo buildQuery('/search') . "\n";
echo buildQuery('/search', q: 'php arrays', page: 2) . "\n";

Output

/search
/search?q=php+arrays&page=2

q and page are not declared parameters, so they are collected into $params as ['q' => 'php arrays', 'page' => 2].

---

Variadic Parameters by Reference

Adding & makes each collected argument a reference to the caller's variable:

<?php
function trimAll(string &...$values): void
{
    foreach ($values as &$value) {
        $value = trim($value);
    }
    unset($value);
}

$name = '  Asha  ';
$city = ' Chennai ';

trimAll($name, $city);

var_dump($name, $city);

Output

string(4) "Asha"
string(7) "Chennai"

Each argument must be a variable. As with other reference parameters, use this sparingly — returning new values is usually clearer.

---

Practical Example: A Formatted Logger

<?php
function logMessage(string $level, string $format, string|int|float ...$values): string
{
    $message = sprintf($format, ...$values);

    return sprintf('[%s] %-7s %s', '2026-10-09 10:15', strtoupper($level), $message);
}

echo logMessage('info', 'User %s logged in from %s', 'asha', '10.0.0.5') . "\n";
echo logMessage('warning', 'Disk usage at %d%%', 91) . "\n";
echo logMessage('error', 'Payment %s failed after %d attempts', 'PAY-889', 3) . "\n";

Output

[2026-10-09 10:15] INFO    User asha logged in from 10.0.0.5
[2026-10-09 10:15] WARNING Disk usage at 91%
[2026-10-09 10:15] ERROR   Payment PAY-889 failed after 3 attempts

Step-by-Step Explanation

1. $level and $format are required; any number of values follow.
2. sprintf($format, ...$values) unpacks the collected values back into separate arguments for sprintf(), which fills the placeholders.
3. %-7s left-aligns the level in a 7-character column so messages line up.
4. The timestamp is fixed here to keep the output predictable; a real logger would use date('Y-m-d H:i').

The variadic parameter lets one function handle messages with zero, one, or many values, with type checking on each value.

---

Legacy Alternative: func_get_args()

Before PHP 5.6 introduced ..., functions read extra arguments with func_get_args():

function oldSum()
{
    return array_sum(func_get_args());
}

This still works, but the signature hides the fact that the function accepts arguments, and there is no type checking. Use variadic parameters in modern code.

---

Common Mistakes

Placing the Variadic Parameter Before Others

function report(string ...$lines, string $title) { }   // compile error

Fix: The variadic parameter must be the last parameter.

Passing an Array Instead of Unpacking It

<?php
function sum(int ...$numbers): int
{
    return array_sum($numbers);
}

$prices = [499, 1299];
echo sum($prices);   // TypeError: an array is not an int

Fix: sum(...$prices).

Forgetting That Zero Arguments Are Allowed

Effect: Code inside the function assumes at least one value (for example, $values[0]) and fails on an empty array.

Fix: Handle the empty case, or require the first value as a normal parameter.

Positional Arguments After Unpacking

Effect: Compile-time error.

Fix: Place normal arguments before ...$array.

---

Best Practices

• Use variadic parameters for "zero or more" or "one or more" values of the same kind.
• Type the variadic parameter so every value is checked.
• Require a first value explicitly when an empty call makes no sense.
• Use ... in calls to unpack arrays instead of call_user_func_array().
• Prefer an explicit array parameter when callers naturally already have an array and the values are not a simple list of arguments.

Official reference: https://www.php.net/manual/en/functions.arguments.php#functions.variable-arg-list

What Is a Variadic Function?

In simple terms: A variadic function accepts any number of arguments. Instead of declaring a fixed list of parameters, you declare one parameter that collects all remaining arguments into an array.

Technically: A parameter prefixed with ... (the splat or spread operator) is a variadic parameter. When the function is called, all remaining positional arguments are collected into an array and assigned to that parameter.

function sum(int ...$numbers): int   // $numbers is an array of all passed integers

Why Variadic Functions Exist

Some operations naturally work on "one or more" or "zero or more" values: adding numbers, joining words, logging a message with any number of details, or finding the maximum. PHP's own max(), min(), printf(), and array_merge() work this way. Variadic parameters let your functions do the same.

---

Syntax

function functionName(Type $required, Type ...$rest)
{
    // $rest is an array of the remaining arguments
}

Example

<?php
function sum(int ...$numbers): int
{
    $total = 0;

    foreach ($numbers as $number) {
        $total += $number;
    }

    return $total;
}

echo sum(1, 2, 3) . "\n";
echo sum(10, 20, 30, 40, 50) . "\n";
echo sum() . "\n";

Output

6
150
0

How It Works

• ...$numbers collects all arguments into an array: sum(1, 2, 3) gives $numbers = [1, 2, 3].
• Calling sum() with no arguments gives an empty array, so the loop does not run and the result is 0.
• The type int applies to each collected argument. Passing a non-integer value that cannot be converted causes a TypeError.

(The body could simply be return array_sum($numbers); — the loop is shown to make the collected array visible.)

---

Combining Regular and Variadic Parameters

Regular parameters come first; the variadic parameter must be last, and there can be only one.

<?php
function joinWords(string $separator, string ...$words): string
{
    return implode($separator, $words);
}

echo joinWords(', ', 'PHP', 'MySQL', 'Laravel') . "\n";
echo joinWords(' | ', 'Home', 'Courses') . "\n";

Output

PHP, MySQL, Laravel
Home | Courses

The first argument always goes to $separator; every argument after it goes into $words.

Requiring at Least One Value

A variadic parameter accepts zero arguments. To require at least one, declare the first value as a normal parameter:

<?php
function maxOf(int $first, int ...$others): int
{
    return max($first, ...$others);
}

echo maxOf(3, 9, 4) . "\n";
echo maxOf(7) . "\n";

Output

9
7

Calling maxOf() with no arguments now throws an ArgumentCountError, which is correct — the maximum of nothing is undefined. Inside the function, ...$others unpacks the array again for max() (explained below).

---

Argument Unpacking: ... in Function Calls

The same ... operator works in the opposite direction in a call: it spreads an array (or other iterable) into separate arguments.

<?php
function sum(int ...$numbers): int
{
    return array_sum($numbers);
}

$cartPrices = [499, 1299];
$extraCharges = [100];

echo sum(...$cartPrices) . "\n";
echo sum(...$cartPrices, ...$extraCharges) . "\n";
echo sum(5, ...$cartPrices) . "\n";

$dateParts = [2026, 10, 15];
$date = new DateTimeImmutable();
echo $date->setDate(...$dateParts)->format('Y-m-d') . "\n";

Output

1798
1898
1803
2026-10-15

How It Works

• sum(...$cartPrices) is equivalent to sum(499, 1299).
• Several arrays can be unpacked in one call, and normal arguments can come before an unpacked array.
• Unpacking works with any function, not only variadic ones: setDate(...[2026, 10, 15]) passes three separate arguments to setDate($year, $month, $day).

Rule: In a call, a normal positional argument cannot come after an unpacked array. sum(...$cartPrices, 5) is a compile-time error ("Cannot use positional argument after argument unpacking"). Put the extra value first, or unpack [5] as another array.

Unpacking Arrays With String Keys (PHP 8.1+)

When an unpacked array has string keys, they are treated as named arguments:

<?php
function createUser(string $name, string $role = 'viewer'): string
{
    return "$name ($role)";
}

$data = ['name' => 'Asha', 'role' => 'admin'];
echo createUser(...$data) . "\n";

Output

Asha (admin)

---

Variadics and Named Arguments

A variadic parameter also collects named arguments that do not match a declared parameter, using the names as string keys:

<?php
function buildQuery(string $path, string|int ...$params): string
{
    return $params === [] ? $path : $path . '?' . http_build_query($params);
}

echo buildQuery('/search') . "\n";
echo buildQuery('/search', q: 'php arrays', page: 2) . "\n";

Output

/search
/search?q=php+arrays&page=2

q and page are not declared parameters, so they are collected into $params as ['q' => 'php arrays', 'page' => 2].

---

Variadic Parameters by Reference

Adding & makes each collected argument a reference to the caller's variable:

<?php
function trimAll(string &...$values): void
{
    foreach ($values as &$value) {
        $value = trim($value);
    }
    unset($value);
}

$name = '  Asha  ';
$city = ' Chennai ';

trimAll($name, $city);

var_dump($name, $city);

Output

string(4) "Asha"
string(7) "Chennai"

Each argument must be a variable. As with other reference parameters, use this sparingly — returning new values is usually clearer.

---

Practical Example: A Formatted Logger

<?php
function logMessage(string $level, string $format, string|int|float ...$values): string
{
    $message = sprintf($format, ...$values);

    return sprintf('[%s] %-7s %s', '2026-10-09 10:15', strtoupper($level), $message);
}

echo logMessage('info', 'User %s logged in from %s', 'asha', '10.0.0.5') . "\n";
echo logMessage('warning', 'Disk usage at %d%%', 91) . "\n";
echo logMessage('error', 'Payment %s failed after %d attempts', 'PAY-889', 3) . "\n";

Output

[2026-10-09 10:15] INFO    User asha logged in from 10.0.0.5
[2026-10-09 10:15] WARNING Disk usage at 91%
[2026-10-09 10:15] ERROR   Payment PAY-889 failed after 3 attempts

Step-by-Step Explanation

1. $level and $format are required; any number of values follow.
2. sprintf($format, ...$values) unpacks the collected values back into separate arguments for sprintf(), which fills the placeholders.
3. %-7s left-aligns the level in a 7-character column so messages line up.
4. The timestamp is fixed here to keep the output predictable; a real logger would use date('Y-m-d H:i').

The variadic parameter lets one function handle messages with zero, one, or many values, with type checking on each value.

---

Legacy Alternative: func_get_args()

Before PHP 5.6 introduced ..., functions read extra arguments with func_get_args():

function oldSum()
{
    return array_sum(func_get_args());
}

This still works, but the signature hides the fact that the function accepts arguments, and there is no type checking. Use variadic parameters in modern code.

---

Common Mistakes

Placing the Variadic Parameter Before Others

function report(string ...$lines, string $title) { }   // compile error

Fix: The variadic parameter must be the last parameter.

Passing an Array Instead of Unpacking It

<?php
function sum(int ...$numbers): int
{
    return array_sum($numbers);
}

$prices = [499, 1299];
echo sum($prices);   // TypeError: an array is not an int

Fix: sum(...$prices).

Forgetting That Zero Arguments Are Allowed

Effect: Code inside the function assumes at least one value (for example, $values[0]) and fails on an empty array.

Fix: Handle the empty case, or require the first value as a normal parameter.

Positional Arguments After Unpacking

Effect: Compile-time error.

Fix: Place normal arguments before ...$array.

---

Best Practices

• Use variadic parameters for "zero or more" or "one or more" values of the same kind.
• Type the variadic parameter so every value is checked.
• Require a first value explicitly when an empty call makes no sense.
• Use ... in calls to unpack arrays instead of call_user_func_array().
• Prefer an explicit array parameter when callers naturally already have an array and the values are not a simple list of arguments.

Official reference: https://www.php.net/manual/en/functions.arguments.php#functions.variable-arg-list

What Is a Variadic Function?

In simple terms: A variadic function accepts any number of arguments. Instead of declaring a fixed list of parameters, you declare one parameter that collects all remaining arguments into an array.

Technically: A parameter prefixed with ... (the splat or spread operator) is a variadic parameter. When the function is called, all remaining positional arguments are collected into an array and assigned to that parameter.

function sum(int ...$numbers): int   // $numbers is an array of all passed integers

Why Variadic Functions Exist

Some operations naturally work on "one or more" or "zero or more" values: adding numbers, joining words, logging a message with any number of details, or finding the maximum. PHP's own max(), min(), printf(), and array_merge() work this way. Variadic parameters let your functions do the same.

---

Syntax

function functionName(Type $required, Type ...$rest)
{
    // $rest is an array of the remaining arguments
}

Example

<?php
function sum(int ...$numbers): int
{
    $total = 0;

    foreach ($numbers as $number) {
        $total += $number;
    }

    return $total;
}

echo sum(1, 2, 3) . "\n";
echo sum(10, 20, 30, 40, 50) . "\n";
echo sum() . "\n";

Output

6
150
0

How It Works

• ...$numbers collects all arguments into an array: sum(1, 2, 3) gives $numbers = [1, 2, 3].
• Calling sum() with no arguments gives an empty array, so the loop does not run and the result is 0.
• The type int applies to each collected argument. Passing a non-integer value that cannot be converted causes a TypeError.

(The body could simply be return array_sum($numbers); — the loop is shown to make the collected array visible.)

---

Combining Regular and Variadic Parameters

Regular parameters come first; the variadic parameter must be last, and there can be only one.

<?php
function joinWords(string $separator, string ...$words): string
{
    return implode($separator, $words);
}

echo joinWords(', ', 'PHP', 'MySQL', 'Laravel') . "\n";
echo joinWords(' | ', 'Home', 'Courses') . "\n";

Output

PHP, MySQL, Laravel
Home | Courses

The first argument always goes to $separator; every argument after it goes into $words.

Requiring at Least One Value

A variadic parameter accepts zero arguments. To require at least one, declare the first value as a normal parameter:

<?php
function maxOf(int $first, int ...$others): int
{
    return max($first, ...$others);
}

echo maxOf(3, 9, 4) . "\n";
echo maxOf(7) . "\n";

Output

9
7

Calling maxOf() with no arguments now throws an ArgumentCountError, which is correct — the maximum of nothing is undefined. Inside the function, ...$others unpacks the array again for max() (explained below).

---

Argument Unpacking: ... in Function Calls

The same ... operator works in the opposite direction in a call: it spreads an array (or other iterable) into separate arguments.

<?php
function sum(int ...$numbers): int
{
    return array_sum($numbers);
}

$cartPrices = [499, 1299];
$extraCharges = [100];

echo sum(...$cartPrices) . "\n";
echo sum(...$cartPrices, ...$extraCharges) . "\n";
echo sum(5, ...$cartPrices) . "\n";

$dateParts = [2026, 10, 15];
$date = new DateTimeImmutable();
echo $date->setDate(...$dateParts)->format('Y-m-d') . "\n";

Output

1798
1898
1803
2026-10-15

How It Works

• sum(...$cartPrices) is equivalent to sum(499, 1299).
• Several arrays can be unpacked in one call, and normal arguments can come before an unpacked array.
• Unpacking works with any function, not only variadic ones: setDate(...[2026, 10, 15]) passes three separate arguments to setDate($year, $month, $day).

Rule: In a call, a normal positional argument cannot come after an unpacked array. sum(...$cartPrices, 5) is a compile-time error ("Cannot use positional argument after argument unpacking"). Put the extra value first, or unpack [5] as another array.

Unpacking Arrays With String Keys (PHP 8.1+)

When an unpacked array has string keys, they are treated as named arguments:

<?php
function createUser(string $name, string $role = 'viewer'): string
{
    return "$name ($role)";
}

$data = ['name' => 'Asha', 'role' => 'admin'];
echo createUser(...$data) . "\n";

Output

Asha (admin)

---

Variadics and Named Arguments

A variadic parameter also collects named arguments that do not match a declared parameter, using the names as string keys:

<?php
function buildQuery(string $path, string|int ...$params): string
{
    return $params === [] ? $path : $path . '?' . http_build_query($params);
}

echo buildQuery('/search') . "\n";
echo buildQuery('/search', q: 'php arrays', page: 2) . "\n";

Output

/search
/search?q=php+arrays&page=2

q and page are not declared parameters, so they are collected into $params as ['q' => 'php arrays', 'page' => 2].

---

Variadic Parameters by Reference

Adding & makes each collected argument a reference to the caller's variable:

<?php
function trimAll(string &...$values): void
{
    foreach ($values as &$value) {
        $value = trim($value);
    }
    unset($value);
}

$name = '  Asha  ';
$city = ' Chennai ';

trimAll($name, $city);

var_dump($name, $city);

Output

string(4) "Asha"
string(7) "Chennai"

Each argument must be a variable. As with other reference parameters, use this sparingly — returning new values is usually clearer.

---

Practical Example: A Formatted Logger

<?php
function logMessage(string $level, string $format, string|int|float ...$values): string
{
    $message = sprintf($format, ...$values);

    return sprintf('[%s] %-7s %s', '2026-10-09 10:15', strtoupper($level), $message);
}

echo logMessage('info', 'User %s logged in from %s', 'asha', '10.0.0.5') . "\n";
echo logMessage('warning', 'Disk usage at %d%%', 91) . "\n";
echo logMessage('error', 'Payment %s failed after %d attempts', 'PAY-889', 3) . "\n";

Output

[2026-10-09 10:15] INFO    User asha logged in from 10.0.0.5
[2026-10-09 10:15] WARNING Disk usage at 91%
[2026-10-09 10:15] ERROR   Payment PAY-889 failed after 3 attempts

Step-by-Step Explanation

1. $level and $format are required; any number of values follow.
2. sprintf($format, ...$values) unpacks the collected values back into separate arguments for sprintf(), which fills the placeholders.
3. %-7s left-aligns the level in a 7-character column so messages line up.
4. The timestamp is fixed here to keep the output predictable; a real logger would use date('Y-m-d H:i').

The variadic parameter lets one function handle messages with zero, one, or many values, with type checking on each value.

---

Legacy Alternative: func_get_args()

Before PHP 5.6 introduced ..., functions read extra arguments with func_get_args():

function oldSum()
{
    return array_sum(func_get_args());
}

This still works, but the signature hides the fact that the function accepts arguments, and there is no type checking. Use variadic parameters in modern code.

---

Common Mistakes

Placing the Variadic Parameter Before Others

function report(string ...$lines, string $title) { }   // compile error

Fix: The variadic parameter must be the last parameter.

Passing an Array Instead of Unpacking It

<?php
function sum(int ...$numbers): int
{
    return array_sum($numbers);
}

$prices = [499, 1299];
echo sum($prices);   // TypeError: an array is not an int

Fix: sum(...$prices).

Forgetting That Zero Arguments Are Allowed

Effect: Code inside the function assumes at least one value (for example, $values[0]) and fails on an empty array.

Fix: Handle the empty case, or require the first value as a normal parameter.

Positional Arguments After Unpacking

Effect: Compile-time error.

Fix: Place normal arguments before ...$array.

---

Best Practices

• Use variadic parameters for "zero or more" or "one or more" values of the same kind.
• Type the variadic parameter so every value is checked.
• Require a first value explicitly when an empty call makes no sense.
• Use ... in calls to unpack arrays instead of call_user_func_array().
• Prefer an explicit array parameter when callers naturally already have an array and the values are not a simple list of arguments.

Official reference: https://www.php.net/manual/en/functions.arguments.php#functions.variable-arg-list