Functions in PHP

A function is a block of code that performs a specific task and can be reused.

Creating Functions

Syntax

function functionName(){
   // code
}

Example

function greet(){
   echo "Welcome to PHP";
}
greet();

Exam Line: Functions increase code reusability and readability.

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Passing Arguments to Functions

1. Pass by Value

• Changes do NOT affect original variable

function add($x){
   $x += 5;
}
$a = 10;
add($a);
echo $a;   // Output: 10

2. Pass by Reference

• Changes affect original variable
• Use & symbol

function add(&$x){
   $x += 5;
}
$a = 10;
add($a);
echo $a;   // Output: 15

Difference Table

Exam Tip: Reference passing is memory efficient.

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Recursive Functions

A recursive function is a function that calls itself until a condition is met.

Example: Factorial

function factorial($n){
   if($n == 1){
      return 1;
   }
   return $n * factorial($n - 1);
}

echo factorial(5);

Output: 120

Important Rules

• Must have a base condition
• Otherwise infinite recursion occurs

Exam Line: Recursive functions require a base condition.

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Advantages of Functions

• Code reusability
• Easy debugging
• Modular programming
• Reduced redundancy