Passing Arguments to a Function by Value in PHP

Passing arguments by value is the default behavior in PHP. When a function receives an argument by value, it gets a copy of that variable’s data. Any changes made inside the function do NOT affect the original variable outside the function.
This provides safety and prevents accidental modifications to data that should remain unchanged.

What Does “Passing by Value” Mean?

When you call a function using pass-by-value:

A new copy of the variable is created
The function works only with this copy
The original variable remains unchanged

This is the opposite of “pass by reference,” where changes are applied directly to the original variable.

Default Behavior in PHP

All function arguments in PHP are passed by value unless specified otherwise.

Example:

function addOne($num) {
    $num = $num + 1;
    echo "Inside function: $num<br>";
}

$value = 10;
addOne($value);

echo "Outside function: $value";

Output:

Inside function: 11  
Outside function: 10

➡ As you can see, the original $value remains unchanged.

Why Use Pass-by-Value?

Prevents accidental modification of important variables
Ensures safer and more predictable code
Useful when you only need the value, not to modify it
Ideal for mathematical calculations & temporary processing

Example: Pass-by-Value with Strings

function changeText($text) {
    $text = "Modified: " . $text;
}

$msg = "Hello PHP";
changeText($msg);

echo $msg; // Output: Hello PHP

Example: Pass-by-Value in Loops

function testLoop($num) {
    $num *= 5;
    return $num;
}

$original = 6;
$result = testLoop($original);

echo $original; // 6
echo $result;   // 30

When Should You Use Pass-by-Value?

When working with constants
When processing temporary variables
When you want to protect original data
When debugging (to avoid side effects)
In pure functions where input should not be altered

Key Takeaways

Default mode in PHP
Function gets a copy, not the original
Changes stay inside the function
Best for safe and clean programming

Citations

🔗 View other articles about PHP:
http://savanka.com/category/learn/php/

🔗 External PHP Documentation:
https://www.php.net/manual/en/