PHP $ xpath->查询循环

I would like to perform a for loop with $xpath->query but it seems to fail at some point .Please i need some guidance.

This is me trying looping

for($i=1 ; $i<8 ;$i++)
{
    for($j=1 ; $j<24 ;$j++)
    $status[] = $xpath->query('//div[@class="datatable"]/table//tbody/tr[$i]/td[$j]/text()');
}

foreach($status as $xpathElement)
{    
    foreach($xpathElement as $nodeKey=>$nodeValue)
    {       
        $arr[] = $nodeValue->textContent;       
    }
}

Because you're using single quotes your resulting query string looks exactly like this (with $i and $j inserted as strings): //div[@class="datatable"]/table//tbody/tr[$i]/td[$j]/text().

To actually insert numbers (stored in $i and $j variables) use double quotes: $xpath->query("//div[@class=\"datatable\"]/table//tbody/tr[$i]/td[$j]/text()");.

Or if you still want to use single quotes, you can write it like this:

$xpath
  ->query('//div[@class="datatable"]/table//tbody/tr[' . $i . ']/td[' . $j . ']/text()');