Does PHP Use Short-Circuit Evaluation to Optimize Conditional Statements?

PHP Short-Circuit Evaluation: Investigating Conditional Shortcuts

Short-circuit evaluation is a common optimization technique implemented in programming languages to improve performance by reducing unnecessary computations. Let's delve into this concept in the context of PHP.

Does PHP Utilize Short-Circuit Evaluation?

The PHP interpreter indeed supports short-circuit evaluation for conditional expressions. In short, when evaluating a logical "AND" (&&) or "OR" (||) expression, PHP stops evaluating subsequent conditions once one of them returns false or true, respectively.

Conditional Evaluation in PHP

To illustrate this behavior, consider the following code:

if (is_valid($string) && up_to_length($string) && file_exists($file)) {
    // ...
}

If is_valid($string) evaluates to false, the PHP interpreter will immediately exit the conditional statement without checking up_to_length($string) or file_exists($file) because the overall result is already determined to be false.

PHP's Efficient Approach

This lazy evaluation approach is advantageous in situations where subsequent conditions are computationally expensive. By avoiding unnecessary calculations, PHP minimizes wasted effort and improves overall performance.

Practical Demonstration

To verify this behavior, consider the following function and conditional:

function saySomething() {
    echo 'hi!';
    return true;
}

if (false && saySomething()) {
    echo 'statement evaluated to true';
}

In this example, despite the presence of the saySomething() function after the logical "AND," the "hi!" message will not be echoed because the condition immediately short-circuits upon evaluating the first expression to false.

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