if(!$pages) if what is not $pages i dont get it

Question

Below is the following code in a pagenation function I am trying to understand the part I dont understand is the if(!pages){ $pages =1)} what are they refering to. if what is not the $pages variable. What i am trying to say is what is the Pages variable being compared if not what. I am confused

if($pages == '')
     {
         global $wp_query;
         $pages = $wp_query->max_num_pages;
         if(!$pages)
         {
             $pages = 1;
         }
     } 

Here is the full function, I am trying to understand it piece by piece so that I can rewrite without the numbers in the pagenation just have right and left.

function kriesi_pagination($pages = '', $range = 2)
{  
     $showitems = ($range * 2)+1;  

     global $paged;
     if(empty($paged)) $paged = 1;

     if($pages == '')
     {
         global $wp_query;
         $pages = $wp_query->max_num_pages;
         if(!$pages)
         {
             $pages = 1;
         }
     }   

     if(1 != $pages)
     {
         echo "<div class='pagination'>";
         if($paged > 2 && $paged > $range+1 && $showitems < $pages) echo "<a href='".get_pagenum_link(1)."'>&laquo;</a>";
         if($paged > 1 && $showitems < $pages) echo "<a href='".get_pagenum_link($paged - 1)."'>&lsaquo;</a>";

         for ($i=1; $i <= $pages; $i++)
         {
             if (1 != $pages &&( !($i >= $paged+$range+1 || $i <= $paged-$range-1) || $pages <= $showitems ))
             {
                 echo ($paged == $i)? "<span class='current'>".$i."</span>":"<a href='".get_pagenum_link($i)."' class='inactive' >".$i."</a>";
             }
         }

         if ($paged < $pages && $showitems < $pages) echo "<a href='".get_pagenum_link($paged + 1)."'>&rsaquo;</a>";  
         if ($paged < $pages-1 &&  $paged+$range-1 < $pages && $showitems < $pages) echo "<a href='".get_pagenum_link($pages)."'>&raquo;</a>";
         echo "</div>\n";
     }
}

Answer 1

if what is not pages fun the code inside the if statement huh.

Your code "globalizes" the $wp_query object so that it is accessible in the scope of the function. Then sets $pages to $wp_query->max_num_pages . Then checks that value to determine whether to execute the if . How that works is a bit tricky but here you go.

PHP considers several things to be FALSE

• the boolean FALSE itself
• the integer 0 (zero)
• the float 0.0 (zero)
• the empty string, and the string "0"
• an array with zero elements
• an object with zero member variables (PHP 4 only)
• the special type NULL (including unset variables)
• SimpleXML objects created from empty tags

If none of those match $pages will be true, which would ordinarily trigger the if to execute but the match is reversed with the ! . So, if $pages is set to some true value then the if condition is false and the if does not run-- leaving $pages alone. If $pages is set to some false value, the if condition is true , it executes, and pages gets set to 1.

Answer 2

There are a couple of parts to this:

• True and False are values that can be saved in variables. This type of value is called Boolean. Instead of if ($a == $b) { ... } you can say $c = ($a == $b); and then later do if ($c) { ... } . This concept of boolean is common to most if not all programming languages.
• In PHP, (but not in all languages), if you treat a non-boolean variable as though it were boolean, (eg by testing it with if , or combine it with and or or ) it will not be an error, and the variable will get converted using certain rules. Basically most things convert to true (they are "truthy"), apart from 0, NULL, Empty Arrays, Empty strings, and a few other things, which convert to false (they are "falsy").

So the if (!$pages) { $pages = 1; } if (!$pages) { $pages = 1; } in your example is saying if the number of pages is zero, make sure there is at least one. It's a shorter way of saying if ($pages == 0) .

Answer 3

The condition checks if $pages is 0 . The boolean values true and false are usually defined by the binaries 1 and 0 respectively. Thus, if(!$pages) means "if the value of $pages evaluates to false (or 0 ) then execute the condition body and set $pages to 1 ". Conversely, if($pages) would mean execute the condition body if $pages > 0 .

Answer 4

I'm not sure what language this is, but it should clearly define what counts as "true" and "false" where boolean expressions are expected. For example, in C, any non-zero integer value is "true"; anything else is "false". Some languages will also define what string values are considered "true" or "false". This is exactly what the if statement in your code is doing.