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<?php

/**

* class QueryTableParser

*

* Very rough class to extract table names from a SQL query.

*

* This class simply looks for specific tokens like FROM, JOIN, UPDATE, INTO

* and collects a list of the very next token after those words.

*

* It doesn't attempt to parse aliases, or any other query structure.

*

* This probably doesn't handle table names with a space in it like `table name`

*

* @author Gavin Towey <gavin@box.com>

* @created 2012-01-01

* @license Apache 2.0 license. See LICENSE document for more info

*

* @todo handle table names with spaces wrapped in backticks or quotes

* @todo stop parsing early if possible -- after the JOIN clause (if any)

* @todo ignore token values inside string literals or backticks

*/

class QueryTableParser {

public $pos;

public $query;

public $len;

public $table_tokens = array(

'from',

'join',

'update',

'into',

);

/**

* parse a query and return an array of table names from it.

*

* @param string $query the sql query

* @return array the list of table names.

*/

public function parse($query) {

$this->query = preg_replace("/\s+/s", " ", $query);

$this->pos = 0;

$this->len = strlen($this->query);

//print "<pre>";

//print "parsing {$this->query}; length {$this->len}\n";

$tables = array();

while ($this->has_next_token()) {

$token = $this->get_next_token();

//print "--> found $token\n";

if (in_array(strtolower($token), $this->table_tokens)) {

$table = $this->get_next_token();

#Handles old style joins

if (preg_match("/,/", $table)) {

while (preg_match("/,/", $table)) {

$table = str_replace(',', '', $table);

if (preg_match("/\w+/", $table)) {

$table = str_replace('`', '', $table);

$tables[$table]=1;

}

$table = $this->get_next_token();

}

if (preg_match("/\w+/", $table)) {

$table = str_replace('`', '', $table);

$tables[$table]=1;

}

}

else {

if (preg_match("/\w+/", $table)) {

$table = str_replace('`', '', $table);

$tables[$table]=1;

}

}

}

}

//print "</pre>";

return array_keys($tables);

}

/**

* return true if we're not at the end of the string yet.

* @return boolean true if there are more tokens to read

*/

private function has_next_token() {

// at end

if ($this->pos >= $this->len) {

return false;

}

return true;

}

/**

* returns the next whitespace separated string of characters

* @return string the token value

*/

private function get_next_token() {

// get the pos of the next token boundary

$pos = strpos($this->query, " ", $this->pos);

//print "get next token {$this->pos} {$this->len} {$pos}\n";

if ($pos === false) {

$pos = $this->len;

}

// found next boundary

$start = $this->pos;

$len = $pos - $start;

$this->pos = $pos + 1;

return substr($this->query, $start, $len);

}

}

?>