Find Unset Local Variables

find-local-vars.php

<?php

$path_to_file = '...';

$file = explode( "\n", file_get_contents( $path_to_file ) );

// Finds local variables that are undeclared.
//
// Doesn't understand foreach() variables, dockblocks, sprintf arguments,
// variables returned by reference from a function like preg_match() or parse_str(),
// assignments that don't start a line, and a few other things.

$set_variables = array();

foreach ( $file as $num => $line ) {
	if ( 0 === strpos( $line, 'function ' ) || $line === '}' ) {
		if ( $line === '}' && $found )
			echo "----------------------------\n\n";

		$found = false;
		$set_variables = array( '$_POST', '$_GET', '$_REQUEST', '$_SERVER', '$GLOBALS' );
		if ( false !== strpos( $line, ' $action ' ) )
			$set_variables[] = '$action';
	}

	if ( preg_match( '/^\s+global (\$[a-zA-Z_\x7f-\xff][, \$a-zA-Z0-9_\x7f-\xff,]*);/', $line, $match ) )
		$set_variables = array_merge( $set_variables, explode( ", ", $match[1] ) );

	if ( preg_match( '/^\s+(\$[a-zA-Z_\x7f-\xff][a-zA-Z0-9_\x7f-\xff]*)\s+=/', $line, $match ) )
		$set_variables[] = $match[1];

	if ( preg_match_all( '/\$[a-zA-Z_\x7f-\xff][a-zA-Z0-9_\x7f-\xff]*/', $line, $variables ) ) {
		foreach ( $variables[0] as $variable ) {
			if ( ! in_array( $variable, $set_variables ) ) {
				$found = true;
				echo "[ $num ] $variable\n    $line\n\n";
			}
		}
	}
}

This is probably easier to use the tokenizer for. That way, you can check if a variable is declared within a block properly.