Why Are Required PHP 8.0 Function Parameters Now Required to Precede Optional Ones?

PHP 8.0 Function Parameter Syntax Changes: Required Parameters Must Precede Optional Ones

PHP 8.0 introduces a deprecation warning when a required function parameter follows an optional parameter. This error occurs because older versions of PHP allowed for this behavior, which didn't make sense since all parameters up to the last required one needed to be specified.

Example:

Consider the following function:

function test_function(int $var1 = 2, int $var2) {
    return $var1 / $var2;
}

In PHP 8.0, this function will throw the following deprecation warning:

Deprecated: Required parameter $var2 follows optional parameter $var1 in...

Reason for Deprecation:

This change ensures that function signatures adhere to the common sense assumption that required parameters should be declared before optional ones. This clarifies function behavior and simplifies analysis using the ReflectionFunctionAbstract class.

Solution:

To resolve this issue, simply remove the default value from the earlier parameters. For the example above, the function would be rewritten as:

function test_function(int $var1, int $var2) {
    return $var1 / $var2;
}

This change should not affect the functionality of the function as it could never be called without declaring all parameters.

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