Find Unset Local Variables

find-local-vars.php

<?php
/**
 * Find unset PHP variables
 *
 * Deals with scope fairly correctly.
 *
 * Known bugs:
 *     - Does not yet support `if: ... endif;` (etc)
 *     - Does not yet support {$a}/${a} (coming soon)
 */

// By default, parse ourself!
if (empty($path_to_file)) {
	$path_to_file = __FILE__;
}

$file = file_get_contents($path_to_file);

// Tokenize
$tokens = token_get_all($file);

// Setup
$errors = array(); // array(array($var, $line), ...)

$last = null;       // Last T_VARIABLE
$last_line = null;  // Where $last was defined
$expecting = false; // Are we expecting a new variable? (After => in foreach, or "as")

$ignore_closeblock = false;
$inherits_scope = false;
$add_on_new_scope = null;

// $defined acts as a stack
// A new array is created for each scope
$defined = array(array());
$current_scope = 0;

foreach ($tokens as $token) {
	if (is_string($token)) {
		// Not sure when it'd be null, but just in case
		if ($token === '=' && $last !== null) {
			$defined[$current_scope][] = $last;
			$last = null;
			$last_line = null;
		}
		elseif ($token === '{') {
			if ($inherits_scope) {
				$defined[] = &$defined[$current_scope];
			}
			else {
				$defined[] = array();
			}

			$current_scope++;
			if ($add_on_new_scope !== null) {
				$defined[$current_scope][] = $add_on_new_scope;
				$add_on_new_scope = null;
			}
		}
		elseif ($token === '}' && !$ignore_closeblock) {
			array_pop($defined);
			$current_scope--;
		}
		elseif ($last !== null) {
			$errors[] = array($last, $last_line);
			$last = null;
			$last_line = null;
		}

		continue;
	}

	switch ($token[0]) {
		case T_WHITESPACE:
			continue;

		// We're about to expect a new variable
		case T_DOUBLE_ARROW: // This includes array('a' => 'b') too, that should be fixed
		case T_AS:
		case T_EMPTY:
		case T_ISSET:
			$expecting = true;
			continue;
		
		// We found a variable!
		case T_VARIABLE:
			// Prefixed with $
			$name = substr($token[1], 1);

			// Are we expecting one?
			if ($expecting) {
				$add_on_new_scope = $name;
				$expecting = false;
				continue;
			}

			// Do we know about it?
			if (in_array(substr($token[1], 1), $defined[$current_scope])) {
				continue;
			}

			// Whoops, we already had a variable, what's this doing here?
			// (Unlikely to ever get here)
			if ($last !== null) {
				$errors[] = array($last, $last_line);
			}

			$last = $name;
			$last_line = $token[2];
			continue;

		// Includes a { in it, ignore that for closing blocks
		case T_DOLLAR_OPEN_CURLY_BRACES:
		case T_CURLY_OPEN:
		case T_STRING_VARNAME:
			$ignore_closeblock = true;

			// more here pls
			continue;

		// All types of assignment
		case T_AND_EQUAL:
		case T_MOD_EQUAL:
		case T_MUL_EQUAL:
		case T_SL_EQUAL:
		case T_SR_EQUAL:
		case T_XOR_EQUAL:
			$defined[$current_scope][] = $last;
			$last = null;
			$last_line = null;
			continue;

		// These have no scope, so we fake one
		case T_DO:
		case T_WHILE:
		case T_IF:
		case T_ELSE:
		case T_FOR:
		case T_FOREACH:
			$inherits_scope = true;

		default:
			if ($last !== null) {
				$errors[] = array($last, $last_line);
				$last = null;
				$last_line = null;
			}
	}
}

foreach ($errors as $error) {
	printf('L%2$d: $%1$s' . PHP_EOL, $error[0], $error[1]);
}

Probably also doesn't deal with assignment correctly, not sure on that.

Added T_EMPTY and T_ISSET to tokens that expect an undefined (more that they don't care, really).