How to turn ast into PHP code

const parser = new engine({
// some options :
parser: {
extractDoc: true,
php7: true,
},
ast: {
withPositions: true,
},
});

// Load a static file (Note: this file should exist on your computer)
const phpcode = fs.readFileSync("./1.php", {
encoding: "utf-8"
});

let ast=parser.parseCode(phpcode);

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now:
How to turn ast into PHP code?