php-parser/doc/3_Other_node_tree_representations.markdown

Other node tree representations

It is possible to convert the AST into several textual representations, which serve different uses.

Simple serialization

It is possible to serialize the node tree using serialize() and also unserialize it using unserialize(). The output is not human readable and not easily processable from anything but PHP, but it is compact and generates quickly. The main application thus is in caching.

Human readable dumping

Furthermore it is possible to dump nodes into a human readable format using the dump method of PhpParser\NodeDumper. This can be used for debugging.

$code = <<<'CODE'
<?php

function printLine($msg) {
    echo $msg, "\n";
}

printLine('Hello World!!!');
CODE;

$parser = (new PhpParser\ParserFactory)->create(PhpParser\ParserFactory::PREFER_PHP7);
$nodeDumper = new PhpParser\NodeDumper;

try {
    $stmts = $parser->parse($code);

    echo $nodeDumper->dump($stmts), "\n";
} catch (PhpParser\Error $e) {
    echo 'Parse Error: ', $e->getMessage();
}

The above script will have an output looking roughly like this:

array(
    0: Stmt_Function(
        byRef: false
        params: array(
            0: Param(
                name: msg
                default: null
                type: null
                byRef: false
            )
        )
        stmts: array(
            0: Stmt_Echo(
                exprs: array(
                    0: Expr_Variable(
                        name: msg
                    )
                    1: Scalar_String(
                        value:

                    )
                )
            )
        )
        name: printLine
    )
    1: Expr_FuncCall(
        name: Name(
            parts: array(
                0: printLine
            )
        )
        args: array(
            0: Arg(
                value: Scalar_String(
                    value: Hello World!!!
                )
                byRef: false
            )
        )
    )
)

JSON encoding

Nodes (and comments) implement the JsonSerializable interface. As such, it is possible to JSON encode the AST directly using json_encode():

$code = <<<'CODE'
<?php

function printLine($msg) {
    echo $msg, "\n";
}

printLine('Hello World!!!');
CODE;

$parser = (new PhpParser\ParserFactory)->create(PhpParser\ParserFactory::PREFER_PHP7);

try {
    $stmts = $parser->parse($code);

    echo json_encode($stmts, JSON_PRETTY_PRINT), "\n";
} catch (PhpParser\Error $e) {
    echo 'Parse Error: ', $e->getMessage();
}

This will result in the following output (which includes attributes):

[
    {
        "nodeType": "Stmt_Function",
        "byRef": false,
        "name": "printLine",
        "params": [
            {
                "nodeType": "Param",
                "type": null,
                "byRef": false,
                "variadic": false,
                "name": "msg",
                "default": null,
                "attributes": {
                    "startLine": 3,
                    "endLine": 3
                }
            }
        ],
        "returnType": null,
        "stmts": [
            {
                "nodeType": "Stmt_Echo",
                "exprs": [
                    {
                        "nodeType": "Expr_Variable",
                        "name": "msg",
                        "attributes": {
                            "startLine": 4,
                            "endLine": 4
                        }
                    },
                    {
                        "nodeType": "Scalar_String",
                        "value": "\n",
                        "attributes": {
                            "startLine": 4,
                            "endLine": 4,
                            "kind": 2
                        }
                    }
                ],
                "attributes": {
                    "startLine": 4,
                    "endLine": 4
                }
            }
        ],
        "attributes": {
            "startLine": 3,
            "endLine": 5
        }
    },
    {
        "nodeType": "Expr_FuncCall",
        "name": {
            "nodeType": "Name",
            "parts": [
                "printLine"
            ],
            "attributes": {
                "startLine": 7,
                "endLine": 7
            }
        },
        "args": [
            {
                "nodeType": "Arg",
                "value": {
                    "nodeType": "Scalar_String",
                    "value": "Hello World!!!",
                    "attributes": {
                        "startLine": 7,
                        "endLine": 7,
                        "kind": 1
                    }
                },
                "byRef": false,
                "unpack": false,
                "attributes": {
                    "startLine": 7,
                    "endLine": 7
                }
            }
        ],
        "attributes": {
            "startLine": 7,
            "endLine": 7
        }
    }
]

The JSON representation may be converted back into a node tree using the JsonDecoder:

<?php

$nodeDecoder = new PhpParser\NodeDecoder();
$ast = $nodeDecoder->decode($json);

Note that not all ASTs can be represented using JSON. In particular:

• JSON only supports UTF-8 strings.
• JSON does not support non-finite floating-point numbers. This can occur if the original source code contains non-representable floating-pointing literals such as 1e1000.

If the node tree is not representable in JSON, the initial json_encode() call will fail.