Increment and Decrement

Increments (++) and decrements (--) are used to conveniently adjust variable values by 1. They are commonly employed in loops to modify loop counters for iterating through arrays or objects. They are also useful for incrementing or decrementing variable values in various algorithms that require sequential data processing or calculations.

Pre-increment and post-increment differ in when the variable's value is incremented relative to its use in an expression:

Pre-increment (++i)
The variable is incremented by 1 before being used in the expression. For example, if i = 5, the expression ++i will first increment i to 6, then return 6.

Post-increment (i++)
The variable is incremented by 1 after being used in the expression. For example, if i = 5, the expression i++ will first return 5, then increment i to 6.

Using Pre-Increment

main


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<?php
// Initialize the variable
$counter = 0;

// Prefix increment
echo ++$counter; // Output: 1
echo ++$counter; // Output: 2
echo ++$counter; // Output: 3

// The variable `$counter` now has the value 3
?>

In this example, the variable $counter is incremented by 1 before its value is used for output. Each subsequent call of ++$counter increases $counter by 1, sequentially outputting 1, 2, and 3.

Using Post-Increment

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<?php
// Initialize the variable
$counter = 0;

// Postfix increment
echo $counter++; // Output: 0
echo $counter++; // Output: 1
echo $counter++; // Output: 2

// The variable `$counter` now has the value 3
?>

In this example, the variable $counter is incremented by 1 after its value is used for output. Each subsequent call of $counter++ uses the current value of $counter for output and then increases $counter by 1, sequentially outputting 0, 1, and 2.

Pre-Increment in a Loop

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<?php
// Initialize the counter variable
$counter = 0;

// `for` loop with prefix increment
for ($i = 0; $i < 5; ++$i) {
    echo $i . " "; // Output the value of the counter
}
?>

In this example, $i starts at 0. After each iteration of the for loop, it is incremented by 1 using the prefix increment ++$i. As a result, the loop outputs numbers from 0 to 4.

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Section 5. Chapter 5