Transform PHP ASTs the easy way. Just as tasty as Yufka, but with different ingredients.


Installation

``
npm install --save gyros
`

IMPORTANT: Gyros is ESM-only. Read more.




Motivation

Gyros is the ideal tool for programmatically making small & simple modifications to your PHP code in JavaScript.

As an introducing example, let's put a function wrapper around all array literals:

`js
import { gyros } from 'gyros'

const source =
$xs = [1, 2, [3, 4]];
$ys = [5, 6];
var_dump([$xs, $ys]);

const result = gyros(source, (node, { update, source }) => {
if (node.kind === 'array') {
update(fun(${source()}))
}
})

console.log(result.toString())
`

Output:
`php
$xs = fun([1, 2, fun([3, 4])]);
$ys = fun([5, 6]);
var_dump(fun([$xs, $ys]));
`

Usage

$3

`ts
function gyros(source, options = {}, manipulator)
`

Transform the string source with the function manipulator, returning an output object.

For every node in the AST, manipulator(node, helpers) fires. The recursive walk is an
in-order traversal, so children get called before their parents. This makes it easier to write nested transforms since transforming parents often requires transforming their children first anyway.

The gyros() return value is an object with two properties:
* code – contains the transformed source code
* map – holds the resulting source map object, as generated by magic-string

Calling .toString() on a Gyros result object will return its source code.

> Pro Tip:
> Don't know how a PHP AST looks like? Have a look at astexplorer.net to get an idea.

$3


All options are, as the name suggests, optional. If you want to provide an options object, its place is between the source code and the manipulator function.

#### Parse Mode
There are two parse modes available: code and eval. The default is eval.

The code parse mode allows to parse PHP code as it appears "in the wild", i.e. with enclosing tags. The default eval mode only parses pure PHP code, with no enclosing tags.

`js
gyros('', { parseMode: 'code' }, (node, helpers) => {
// Parse the source as mixed HTML/PHP code
})
`

#### PHP Parser Options
Any options for the underlying php-parser can be passed to options.phpParser:

`js
gyros(source, { phpParser: { parser: { suppressErrors: true } } }, (node, helpers) => {
// Parse the source in loose mode
})
`

#### Source Maps
Gyros uses magic-string under the hood to generate source maps for your code modifications. You can pass its source map options as options.sourceMap:

`js
gyros(source, { sourceMap: { hires: true } }, (node, helpers) => {
// Create a high-resolution source map
})
`

$3


The helpers object passed to the manipulator function exposes the following methods. All of these methods handle the current AST node (the one that's passed to the manipulator as its first argument).

However, all of these methods take an AST node as an optional first parameter if you want to access other nodes.

> Example:
> `js
> gyros('$x = 1', (node, { source }) => {
> if (node.kind === 'assign') {
> // node refers to the $x = 1 Expression
> source() // returns "$x = 1"
> source(node.right) // returns "1"
> }
> })
> `


#### source()
Return the source code for the given node, including any modifications made to
child nodes:

`js
gyros('(true)', (node, { source, update }) => {
if (node.kind === 'boolean') {
source() // returns "true"
update('false')
source() // returns "false"
}
})
`

#### update(replacement)
Replace the source of the affected node with the replacement string:

`js
const result = gyros('4 + 2', (node, { source, update }) => {
if (node.kind === 'bin') {
update(source(node.left) + source(node.right))
}
})

console.log(result.toString())
`

Output:
`php
42
`

#### parent(levels = 1)
From the starting node, climb up the syntax tree levels times. Getting an ancestor node of the program root yields undefined.

`js
gyros('$x = [1]', (node, { parent }) => {
if (node.kind === 'number') {
// node refers to the 1 number literal
parent() // same as parent(1), refers to the 1 as an array element
parent(2) // refers to the [1] expression
parent(3) // refers to the $x = [1] assignment expression
parent(4) // refers to the $x = [1] statement
parent(5) // refers to the program as a whole (root node)
parent(6) // yields undefined, same as parent(6), parent(7) etc.
}
})
`

#### External Helper Access

Tip: If you want to extract manipulation behavior into standalone functions, you can access the helpers directly on the gyros instance (e.g. gyros.source()) where they are not bound to a specific node:

`js
// Standalone function, increments node's value if it's a number
const increment = node => {
if (node.kind === 'number') {
gyros.update(node, String(Number(node.value) + 1))
}
}

const result = gyros('$x = 1', node => {
increment(node)
})

console.log(result.toString())
`
Output:
`php
$x = 2
`

$3


The manipulator function may return a Promise. If it does, Gyros will wait for that to resolve, making the whole gyros() function return a Promise resolving to the result object (instead of returning the result object directly):

`js
import got from 'got' // see www.npmjs.com/package/got

const source =
$content = curl("https://example.com")

const deferredResult = gyros(source, async (node, { source, update }) => {
if (node.kind === 'call' && node.what.kind === 'name' && node.what.name === 'curl') {
// Replace all curl() calls with their actual content

// Get the URL (will only work for simple string literals)
const url = node.arguments[0].value

// Fetch the URL's contents
const contents = (await got(url)).body

// Replace the cUrl() call with the fetched contents
update(JSON.stringify(contents))
}
})

// Result is not available immediately, we need to await it
deferredResult.then(result => {
console.log(result.toString())
})
`

Output:
`php
$content = "\n\n[...]\n"
`

> Note: You have to return a promise if you want to commit updates asynchronously. Once the manipulator function is done running, any update()` calls originating from it will throw an error.