How Does PHP's Short-Circuit Evaluation Optimize Logical Operations?

PHP's Short-Circuit Evaluation

Short-circuit evaluation is a mechanism that optimizes code execution by skipping unnecessary operations based on the evaluation of previous conditions. In PHP, short-circuit evaluation applies to logical operators && (AND) and || (OR).

When the && operator is used, if the first operand evaluates to false, the remaining operands are not evaluated, as the overall result will also be false. Similarly, for the || operator, if the first operand evaluates to true, the remaining operands are not evaluated as the overall result will be true.

Returning to the original code snippet:

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

If is_valid($string) returns false, PHP's short-circuit evaluation will prevent the evaluation of up_to_length($string) and file_exists($file) because the result is already determined to be false.

This behavior is inherent to PHP's "lazy" evaluation. It aims to streamline code execution by only performing necessary operations based on the outcome of earlier conditions.

For instance, consider the following code:

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

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

In this case, even though saySomething is a function that outputs "hi!", it will not be executed because false && will short-circuit the evaluation, making the overall result false.

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