in php/src/ru/adelf/idea/dotenv/php/PhpEnvironmentCallsVisitor.java [31:44]
private void visitFunction(FunctionReference expression) {
if(!PhpPsiHelper.isEnvFunction(expression)) return;
PsiElement[] parameters = expression.getParameters();
if(parameters.length == 0) return;
if(!(parameters[0] instanceof StringLiteralExpression)) return;
String key = ((StringLiteralExpression)parameters[0]).getContents();
collectedItems.add(new KeyUsagePsiElement(key, expression));
}