PHP判断邮箱格式，不用正规

mixed filter_var ( mixed $variable [, int $filter = FILTER_DEFAULT [, mixed $options ]] )
filter_var — Filters a variable with a specified filter
(PHP 5 >= 5.2.0)

Parameters

variable

    Value to filter.
filter

    The ID of the filter to apply. The Types of filters manual page lists the available filters.
options

    Associative array of options or bitwise disjunction of flags. If filter accepts options, flags can be provided in "flags" field of array. For the "callback" filter, callable type should be passed. The callback must accept one argument, the value to be filtered, and return the value after filtering/sanitizing it.

        // for filters that accept options, use this format
    $options = array(
        'options' => array(
            'default' => 3, // value to return if the filter fails
            // other options here
            'min_range' => 0
        ),
        'flags' => FILTER_FLAG_ALLOW_OCTAL,
    );
    $var = filter_var('0755', FILTER_VALIDATE_INT, $options);

    // for filter that only accept flags, you can pass them directly
    $var = filter_var('oops', FILTER_VALIDATE_BOOLEAN, FILTER_NULL_ON_FAILURE);

    // for filter that only accept flags, you can also pass as an array
    $var = filter_var('oops', FILTER_VALIDATE_BOOLEAN,
                      array('flags' => FILTER_NULL_ON_FAILURE));

    // callback validate filter
    function foo($value)
    {
        // Expected format: Surname, GivenNames
        if (strpos($value, ", ") === false) return false;
        list($surname, $givennames) = explode(", ", $value, 2);
        $empty = (empty($surname) || empty($givennames));
        $notstrings = (!is_string($surname) || !is_string($givennames));
        if ($empty || $notstrings) {
            return false;
        } else {
            return $value;
        }
    }
    $var = filter_var('Doe, Jane Sue', FILTER_CALLBACK, array('options' => 'foo'));
    ?>

Returns the filtered data, or FALSE if the filter fails.

//echo  true == filter_var('xx@qq.com', FILTER_VALIDATE_EMAIL) ? 'email' : 'not email'; exit;

http: //php.net/manual/en/function.filter-var.php