Hoisting¶
Hoisting is a language feature where declarations are automatically moved to the top of their scope before code execution. It is notably a JavaScript feature and not a PHP feature.
PHP does not support hoisting for variables: a variable must be assigned before it is read, or it will be undefined.
PHP functions are pre-compiled and can be called before their textual declaration in the same file, which may look like hoisting but is actually the result of PHP’s two-pass compilation model.
PHP classes are not hoisted either: a class must be declared, autoloaded, before it is instantiated.
<?php
// This works: functions are pre-compiled
greet();
function greet() { echo 'Hello'; }
// This does NOT work: variables are not hoisted
echo $message; // Undefined variable
$message = 'Hello';
?>
See also Hoisting (MDN).
Related : Class Hoisting, Class Autoloading, Undefined, Compile, Cache, Order Of Execution
