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Q:

abstract syntax tree - How to use PHP-Parser to get the global variables name and change it

Hey everyone,

I'm currently working on a project where I have to analyze PHP code and perform certain modifications to it. I stumbled upon PHP-Parser, a great library for parsing PHP code and generating an abstract syntax tree (AST). However, I'm facing a little issue and I could really use some help from the community.

What I'm trying to achieve is to extract the names of global variables from the AST and then modify them. I've looked into the PHP-Parser documentation, but I couldn't find a clear example or explanation for this specific task.

It would be really helpful if someone could guide me on how to use PHP-Parser to get the names of global variables from the AST and also provide a way to modify them. Any code snippets or examples would be greatly appreciated.

Thanks in advance!

All Replies

hoeger.archibald

Hey there!

I've also had my fair share of experience using PHP-Parser to analyze and modify PHP code, so I can definitely share some insights on your question.

To retrieve global variable names from the AST and apply changes, you can leverage the power of PHP-Parser and its visitor pattern capability. Here's an approach you can take:

php
class GlobalVariableVisitor extends PhpParser\NodeVisitorAbstract
{
public $globalVariables = [];

public function enterNode(PhpParser\Node $node)
{
if ($node instanceof PhpParser\Node\Expr\Variable && $this->isGlobalVariable($node)) {
$this->globalVariables[] = $node->name->name;
}
}

private function isGlobalVariable(PhpParser\Node\Expr\Variable $node): bool
{
$parentNode = $node->getAttribute('parent');

if ($parentNode instanceof PhpParser\Node\Stmt\Global_) {
return true;
}

// Add more conditions to determine if the variable is global
// For instance, you can check if it's outside any function or class

return false;
}
}

$code = "..."; // Your PHP code snippet goes here

$parser = (new PhpParser\ParserFactory)->create(PhpParser\ParserFactory::PREFER_PHP7); // Adjust PHP version if required
$traverser = new PhpParser\NodeTraverser();

$globalVisitor = new GlobalVariableVisitor();
$traverser->addVisitor($globalVisitor);

$ast = $parser->parse($code);
$traverser->traverse($ast);

$globalVariables = $globalVisitor->globalVariables; // Store the global variable names

foreach ($globalVariables as $variable) {
// Go ahead and make the desired modifications to the global variables
// You can update their names or implement any other changes as per your requirements
}


In this solution, the `GlobalVariableVisitor` class extends `PhpParser\NodeVisitorAbstract` and overrides the `enterNode` method. By checking if the node is an `Expr\Variable` and meets certain conditions defined in the `isGlobalVariable` method, you can identify global variables. If a global variable is found, its name is added to the `$globalVariables` array.

Once the AST traversal is complete, you can iterate through the `$globalVariables` array to apply the needed modifications to the global variables.

I hope this approach helps you! Feel free to ask if you have any further queries or clarifications.

lilian27

Hello!

I've had the opportunity to work with PHP-Parser in a similar scenario, and I can definitely assist you with your question.

To extract global variable names from the AST and apply modifications, you can implement a visitor pattern using PHP-Parser. Here's how you can go about it:

php
class GlobalVariableVisitor extends PhpParser\NodeVisitorAbstract
{
public $globalVariables = [];

public function enterNode(PhpParser\Node $node)
{
if ($node instanceof PhpParser\Node\Expr\Variable && $this->isGlobalVariable($node)) {
$this->globalVariables[] = $node->name->name;
}
}

private function isGlobalVariable(PhpParser\Node\Expr\Variable $node): bool
{
$parent = $node->getAttribute('parent');

// Check if variable is global based on parent node
if ($parent instanceof PhpParser\Node\Stmt\Global_) {
return true;
}

// You can add more conditions to determine global variables, like checking if it's outside any function or class

return false;
}
}

$code = "..."; // Insert your PHP code here

$parser = (new PhpParser\ParserFactory)->create(PhpParser\ParserFactory::PREFER_PHP7); // Adjust PHP version if needed
$traverser = new PhpParser\NodeTraverser();

$globalVisitor = new GlobalVariableVisitor();
$traverser->addVisitor($globalVisitor);

$ast = $parser->parse($code);
$traverser->traverse($ast);

$globalVariables = $globalVisitor->globalVariables; // Contains global variable names

foreach ($globalVariables as $variable) {
// Perform your desired modifications to the global variables
// You can change the variable name or apply any other necessary changes
}


In this example, the `GlobalVariableVisitor` class extends `PhpParser\NodeVisitorAbstract` and overrides the `enterNode` method. It checks if the node is an `Expr\Variable` and if it meets any conditions you define to determine if it's a global variable (e.g., outside any function or class, marked with `global` statement, etc.). If the conditions are met, the variable name is added to the `$globalVariables` array.

After traversing the AST, you can iterate through the `$globalVariables` array for making the necessary modifications to the global variables.

Hope this helps you out! Feel free to ask if you have any further questions.

brown29

Hey there,

I've actually used PHP-Parser for a similar purpose before. To get the names of global variables from the AST, you can make use of the Visitor pattern provided by PHP-Parser.

Here's how you can do it:

php
class GlobalVarVisitor extends PhpParser\NodeVisitorAbstract
{
public $globalVariables = [];

public function enterNode(PhpParser\Node $node)
{
if ($node instanceof PhpParser\Node\Expr\Variable && $node->name instanceof PhpParser\Node\Identifier) {
$this->globalVariables[] = $node->name->name;
}
}
}

$code = "..."; // Your PHP code here

$parser = (new PhpParser\ParserFactory)->create(PhpParser\ParserFactory::PREFER_PHP7); // Adjust the PHP version based on your code
$traverser = new PhpParser\NodeTraverser;

$visitor = new GlobalVarVisitor;
$traverser->addVisitor($visitor);

$ast = $parser->parse($code);
$traverser->traverse($ast);

$globalVariables = $visitor->globalVariables; // Array of global variable names

foreach ($globalVariables as $variable) {
// Perform your modifications to the global variables here
// For example, you can change the variable name to something else
}


This way, the `GlobalVarVisitor` class will traverse the AST and whenever it encounters an `Expr\Variable` node with an `Identifier`, it adds the name of the variable to the `$globalVariables` array.

You can then iterate over the array and make your desired modifications to the global variables.

I hope this helps! Let me know if you have any questions.

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