Can PHP Class Properties Now be Initialized with Simple Expressions?

Constant Scalar Expressions: Resolving Syntax Errors in PHP Class Property Declarations

According to PHP documentation, class properties can be initialized with constant values that can be evaluated during compilation. However, initializing properties with simple expressions like "4 1" has historically resulted in syntax errors.

This restriction stemmed from the inability of PHP to evaluate such expressions during compilation, as they relied on runtime information. However, as of PHP 5.6, a new feature called constant scalar expressions has emerged.

Constant scalar expressions allow scalar expressions composed of numeric and string literals or constants to be used in contexts that previously required static values. This includes constant and property declarations, as well as default function arguments.

Thus, the following code, which previously caused syntax errors, is now valid:

<code class="php">public $var = array(
    1 => 4,
    2 => (4 + 1),
);

public $var = 4 + 1;</code>

This change addresses the limitation of not allowing any calculated expressions, regardless of their ability to be evaluated at compile time. Simple calculations like "4 1" are now permitted, enabling greater flexibility in class property declarations.

The above is the detailed content of Can PHP Class Properties Now be Initialized with Simple Expressions?. For more information, please follow other related articles on the PHP Chinese website!