PHP Class Initialization Conundrum: Evaluating Expressions in Property Declarations

The PHP documentation dictates that class property declarations can be initialized with constant values. However, users have encountered syntax errors when attempting to initialize arrays with non-constant expressions.

Syntax Error Example:

public $var = array(
    1 => 4,
    2 => (4 1), // Syntax error
);

Underlying Issue:

The error stems from a limitation in PHP 5.5 and earlier versions, where only constant values were allowed in property declarations. This includes values that can be evaluated at compile time. However, the use of calculated expressions, like "4 1," was prohibited.

Resolution in PHP 5.6:

This limitation was lifted in PHP 5.6 with the introduction of constant scalar expressions. This feature allows for the following syntax:

public $var = array(
    1 => 4,
    2 => (4 1),
);

public $var = 4 1;

Conclusion:

The syntax error encountered in earlier versions of PHP when initializing class properties with non-constant expressions has been resolved in PHP 5.6 and later versions. Constant scalar expressions now enable developers to initialize properties with calculated values that can be evaluated at compile time.