How is it implemented in the generator that only one object is contained in the current file?

Generator in PHP is implemented as an iterator that allows pausing the execution of a function and resuming it later. When a generator is used in a foreach loop, it works with a single Generator object at any given time. Each time yield is called, the function "remembers" its state (local variables, execution position) and returns a value, generating an iteration element. On the next iteration of the foreach loop, the function continues execution from where it left off. Essentially, the Generator object is a stateful object that manages the iteration state.

<?php

function myGenerator() {
    yield 1; // The function pauses, returning 1
    echo "Continuing after 1\n";
    yield 2; // The function pauses, returning 2
    echo "Continuing after 2\n";
    yield 3; // The function pauses, returning 3
}

$generator = myGenerator(); // Creates a Generator object

foreach ($generator as $value) {
    echo "Received value: " . $value . "\n";
}

// At any moment, the variable $generator contains a single Generator object.
// It manages the iteration process over the generated values.

?>

Thus, a single Generator object encapsulates the state and logic for step-by-step data retrieval, allowing the processing of potentially large data sets without loading them entirely into memory.