follow value of variable in php script

[subabrain]

Hi, i just want to ask if its possible to follow a variable through a php script?

For example:

$val = "test"; $val2 = $val; echo $val2;

I just found the traverse - but how can i do that exactly?

I could do this with regex - but i want to know if its working with the php parser too?

Thanks and Nice Time!

[TomasVotruba]

I use this approach to get property uses in code:

https://github.com/rectorphp/rector/blob/9db613e92ee8c2f5f390937d856a25116b9b1071/packages/Php/src/Rector/Property/CompleteVarDocTypePropertyRector.php#L142-L153

$propertyAssignNodes = $this->betterNodeFinder->find([$classNode], function (Node $node) use (
    $propertyName
): bool {
    if ($node instanceof Assign) {
        if ($node->var instanceof PropertyFetch) {
            // is property match
            return $this->isName($node->var, $propertyName);
        }
    }
    return false;
});

Basically use native NodeFinder and find all variable with that name looking for assigs.

What exactly is your goal? Similar analysis does PHPStan and Rector builds on top of that.

[subabrain]

Hello and Thanks!

sorry but i didnt get it to work ... maybe you can give an example - thanks a lot!

[TomasVotruba]

What is your goal actually? There might be a better solution.

[subabrain]

ok - here an example:

<?php

$var1 = "some_value"; //First assigned Value
$var2 = $var1; //The first variable ($var1) is assigned to $var2

//...

//Now i will echo the last Variable is assigned to the first one
echo $var2;

//Now i want to get out the value of the first assigned variable
//I could do this with regex but if i have the following Construct:

class test {

    public $var1 = "first";
	public $var2;
	
	public function test() {
	
		$this->var2 = $this->var1;
		
	}
	
	public function echo_it() {
	
		echo $this->var2;
	
	}

}

$inst = new test();
$inst->test();
$inst->echo_it();

?>

[TomasVotruba]

I see. So your goal is to get value of echo $var2;, resp. echo $this->var2;?

[subabrain]

yes thats it 👍

[TomasVotruba]

I tried Rector + PHPStan to resolve the value, but unfortunatelly PHPStan is not capable to analyze the value.

Here is code I used:
https://github.com/rectorphp/rector/compare/analasis-example?expand=1#diff-3fd2b223ed0f173609588cfd28904e34

In that way, you'd have to write own NodeScopeResolver - https://github.com/phpstan/phpstan/blob/master/src/Analyser/NodeScopeResolver.php, or extend it.

[TomasVotruba]

What is your ultimate goal to do with the value?

[subabrain]

hey thanks a lot - but how to ge a node from the code? Thanks!

[TomasVotruba]

I started with Documentation: https://github.com/nikic/PHP-Parser/blob/master/doc/2_Usage_of_basic_components.markdown#node-traversation

I go through one-change example in this post: How to change PHP code with Abstract Syntax Tree

[subabrain]

okay - i see - but i get the following error:

Fatal error: Uncaught Error: Call to a member function getNodeStaticType() on null in E:\xampp\htdocs\rector\src\Rector\TypeAnalyzerTrait.php:76
Stack trace:
#0 E:\xampp\htdocs\rector\utils\showcase\src\GetStringValueRector.php(29): Rector\Rector\AbstractRector->getStaticType(Object(PhpParser\Node\Stmt\Expression))
#1 E:\xampp\htdocs\rector\utils\showcase\src\GetStringValueRector.php(52): Rector\Showcase\GetStringValueRector->refactor(Object(PhpParser\Node\Stmt\Expression))
#2 {main}
thrown in E:\xampp\htdocs\rector\src\Rector\TypeAnalyzerTrait.php on line 76

maybe you can help me a last time - thx a lot!

[TomasVotruba]

Open issue at Rector with full code, so we don't spam here

[subabrain]

ok - sorry ill do that ;)

[nikic]

Closing this as out of scope for this library. Other libraries provide support for this on top of this one, e.g. various static analyzers. https://github.com/ircmaxell/php-cfg is also worth mentioning, which tracks variable assignments in SSA form.