framework/web/ErrorHandler.php
public function renderCallStackItem($file, $line, $class, $method, $args, $index)
    {
        $lines = [];
        $begin = $end = 0;
        if ($file !== null && $line !== null) {
            $line--; // adjust line number from one-based to zero-based
            $lines = @file($file);
            if ($line < 0 || $lines === false || ($lineCount = count($lines)) < $line) {
                return '';
            }

            $half = (int) (($index === 1 ? $this->maxSourceLines : $this->maxTraceSourceLines) / 2);
            $begin = $line - $half > 0 ? $line - $half : 0;
            $end = $line + $half < $lineCount ? $line + $half : $lineCount - 1;
        }

        return $this->renderFile($this->callStackItemView, [
            'file' => $file,
            'line' => $line,
            'class' => $class,
            'method' => $method,
            'index' => $index,
            'lines' => $lines,
            'begin' => $begin,
            'end' => $end,
            'args' => $args,
        ]);
    }
public function renderCallStackItem($file, $line, $class, $method, $args, $index)
    {
        $lines = [];
        $begin = $end = 0;
        if ($file !== null && $line !== null) {
            $line--; // adjust line number from one-based to zero-based
            $lines = @file($file);
            if ($line < 0 || $lines === false || ($lineCount = count($lines)) < $line) {
                return '';
            }

            $half = (int) (($index === 1 ? $this->maxSourceLines : $this->maxTraceSourceLines) / 2);
            $begin = $line - $half > 0 ? $line - $half : 0;
            $end = $line + $half < $lineCount ? $line + $half : $lineCount - 1;
        }

        return $this->renderFile($this->callStackItemView, [
            'file' => $file,
            'line' => $line,
            'class' => $class,
            'method' => $method,
            'index' => $index,
            'lines' => $lines,
            'begin' => $begin,
            'end' => $end,
            'args' => $args,
        ]);
    }
Renders a single call stack element.
@param string|null $file name where call has happened.
@param int|null $line number on which call has happened.
@param string|null $class called class name.
@param string|null $method called function/method name.
@param array $args array of method arguments.
@param int $index number of the call stack element.
@return string HTML content of the rendered call stack element.