PHP Interview Questions And Answers

Using the HTTP Content-Type Header

But how do we check to see if a webpage is an HTML page? Clearly we can’t just look at the URL by itself, because a PHP page, JSP page, etc. are all HTML pages, but the file extension does not tell us that. Well, once again we can use the HTTP headers to our advantage – in this case, we just have to take a look at the HTTP Content Type header.
And, if the Content-Type header is equal to “text/html”, then we know that we are dealing with an HTML page. But if the Content-Type header for the URL is not equal to “text/html”, then we know that we are dealing with a single file resource, and we can just return the size.
Let’s write some code in PHP that will tell us if a given URL is actually an HTML page by checking the HTTP headers. Here is a PHP function that will do that for us:

function check_if_html($url){
     $ch = curl_init($url);

     curl_setopt($ch, CURLOPT_RETURNTRANSFER, TRUE);
     curl_setopt($ch, CURLOPT_HEADER, TRUE);
     curl_setopt($ch, CURLOPT_NOBODY, TRUE);

     $data = curl_exec($ch);
     $contentType = curl_getinfo($ch, CURLINFO_CONTENT_TYPE );

     curl_close($ch);
     
     if (strpos($contentType,'text/html') !== false)
   return TRUE;  // this is HTML, yes!
  else
     return FALSE;
}

In the code above, we just use a simple cURL connection to the URL to retrieve the headers, and then check the contentType header to see if it has the text “text/html”. If it does, then we return true, otherwise we return false.
Then, we can add some code that will actually call the function to determine if a URL points to just a single resource file:

/*
check to see if the URL points to an HTML page,
if it doesn't then we are dealing with a single
file resource:
*/
if (!check_if_html($URL))
{
$totalSize = get_remote_file_size($URL);

echo "Final Total Download Size: $totalSize Bytes ";

$totalNumResources += 1;  //single resource is an HTTP request

echo "  Final total HTTP requests: $totalNumResources" ;

return;
}

How to find the total number of HTTP requests

We mentioned that we would need to find the total number of HTTP requests generated by a given URL – let’s figure out how to write some code that will do that for us. It’s clear that we must have some variable that maintains a total count of all HTTP requests, and this variable will be incremented as we come across more and more HTTP requests.
We know that images will be wrapped in an “img” tag – so if we just do a search for all img tags we can take a look at the src attribute, and find the size of any given image. For each image we find, we can increment the variable that holds the total count of the HTTP requests. We can also do the same for CSS files – they will be referenced inside “link” tags, and also for JavaScript files, which will be referenced inside “script” tags.
We will need to use the simple HTML DOM parser that we discussed earlier in order to find all of the references to CSS, Javascript, and image files. Here’s what the code looks like – note that we are using the simple HTML DOM library functionality to parse through the HTML. Also note that we are using a variable called $totalNumResources to hold the total number of resources, and another variable called $totalSize to hold the total size of all of the resources:

include('simple_html_dom.php');

$URL = $argv[1];

// Create DOM from URL or file
$html = file_get_html($URL);

// find all images!!
foreach($html->find('img') as $element){

    $size = get_remote_file_size($element->src);
  
    $totalSize = $totalSize + $size;  
    
    $totalNumResources += 1;

    /*
    echo "Total Size So Far: $totalSize.\n"; 
    
    echo "total resources: $totalNumResources .\n"; 

           echo "IMAGE SIZE: $size.\n";

           echo "$element->src.\n";
       */
}

// find all CSS files
foreach($html->find('link') as $element)
{
    if (strpos($element->href,'.css') !== false) {

    $size = retrieve_remote_file_size($element->href);
    
     echo "SIZE: $size.\n";

     $totalSize = $totalSize + $size; 
        
     $totalNumResources += 1;
     }
}

// find all script tags
foreach($html->find('script') as $element)
{
  //make sure this is javascript
  if (strpos($element->src,'.js') !== false) {
    $size = get_remote_file_size($element->src);
   
     echo " Javascript SIZE: $size.\n"; 

     $totalSize = $totalSize + $size;   
       
      $totalNumResources += 1;
   }
}