<?php

	Class safePDO_Flyweight extends PDO {

		public $options;
		public $tokens;

		public static function exception_handler($exception) {
			// Output the exception details
			die('<h1>Database connection error<p>' . $exception->getMessage() . '</p>');
		}

		// PDO constructor is public so we can't make this private and uninstantiable
		public function __construct($dsn, $username='', $password='', $driver_options=array()) {

			// Temporarily change the PHP exception handler while we . . .
			set_exception_handler(array(__CLASS__, 'exception_handler'));

			// Find out who tried to call the constructor
			$chain = debug_backtrace();
			$caller = $chain[1]['class'];

			// Enforce SprocketPDO_Factory creation
			if ('SprocketPDO_Factory' == $caller) {

				// . . . create a PDO object
				parent::__construct($dsn, $username, $password, $driver_options);

			} else {
				throw new Exception('Cannot directly instantiate. Please use SprocketPDO_Factory');
			}

			// Make the options available
			$this->options = $driver_options;

			// Define the PDO Statement class
			$this->setAttribute(PDO::ATTR_STATEMENT_CLASS, array('extendedPDOStatement', array($this)));

			// Change the exception handler back to whatever it was before
			restore_exception_handler();
		}

		public function prepare($sql) {
			$tokens = array();

			// Check if the option is enabled
			if (true === $this->options['singleTokenMultiParams']) {

				// Parse the SQL query for placeholders
				preg_match_all("/(\:\w+)/", $sql,  $matches, PREG_PATTERN_ORDER);
				foreach($matches[1] as $index=>$token) {
					$tokens[$token]++;
				}

				// For each placeholder
				foreach($tokens as $token=>$count) {

					// Check if the placeholder is repeated
					if ($count > 1) {

						// Find where to start searching (after the first occurrence)
						$start = strpos($sql, $token);
						$length = strlen($token);

						// Replace each additional occurrence with a unique placeholder

						do {
							$start = strpos($sql, $token, $start+1);
							if (false !== $start) {
								$loop++;
								$sql = substr_replace($sql, $token . '_' . $loop, $start, $length);
							}
						} while(false !== $start);
					}
				}
			}

			// Call the standard prepare method
			$pdoStatement = parent::prepare($sql);

			// Store the tokens used with this query
			$this->tokens[$pdoStatement->queryString] = $tokens;

			return $pdoStatement;
		}

	}

?>