PHP escape for SQL

/**
 * Correctly quotes a string so that all strings are escaped. We prefix and append
 * to the string single-quotes.
 * An example is  escape ( "Don't bother",magic_quotes_runtime () );
 *
 * @param str			the string to quote
 * @param [magic_quotes]	if $s is GET/POST var, set to get_magic_quotes_gpc().
 *
 * @return  quoted string to be sent back to database
*/
function escape ( $str, $magic_quotes = false )
{
		switch ( gettype ( $str ) )
		{
			case 'string'	:
				$replaceQuote = "\\'"; 	/// string to use to replace quotes
				if ( ! $magic_quotes ) {

					if ( $replaceQuote [ 0 ] == '\\' ){
						// only since php 4.0.5
						$str = seo_str_replace ( array ( '\\', "\0" ), array ( '\\\\', "\\\0" ), $str );
						//$s = str_replace("\0","\\\0", str_replace('\\','\\\\',$s));
					}
					return  "'" . str_replace ( "'", $replaceQuote, $str ) . "'";
				}

				// undo magic quotes for "
				$str = str_replace ( '\\"','"', $str );

				if ( $replaceQuote == "\\'" ) {// ' already quoted, no need to change anything
					return "'$str'";
				}
				else {// change \' to '' for sybase/mssql
					$str = str_replace ( '\\\\','\\', $str );
					return "'" . str_replace ( "\\'", $treplaceQuote, $str ) . "'";
				}
			break;
			case 'boolean'	:	$str = ($str === FALSE) ? 0 : 1;
						return $str;
				break;
			case 'integer'	:	$str = ($str === NULL) ? 'NULL' : $str;
						return $str;
				break;
			default		:	$str = ($str === NULL) ? 'NULL' : $str;
						return $str;
				break;
		}
}