Php提取数组值

I have an array structure like below.

//var_dump($data):
array(5) { 
    [0]=> string(1) "1" 
    [1]=> string(1) "2" 
    [2]=> string(4) "4=13" 
    [3]=> string(1) "4" 
    [4]=> string(3) "1=4" 
}

Here value 1 and 4 has extension. So I need to get those values.

i.e Final output should be

$data = array(1,4);

$array = array("1", "2", "4=13", "4", "1=4");
$keys = array();
foreach ($array as $value) {
    if (strpos($value, "=") !== false) {
        list($key, $_) = explode("=", $value, 2);
        $keys[] = (int) $key;
    }
}
sort($keys);
var_dump($keys); // array(1, 4)