My Function Logic

[graham23s]

Hi Guys,

 

i'm trying to understand the logic here in the code i have written:

 

function:

 

<?php
  function is_valid_image_file($var_website_image_name)
  { 
    // this takes away - 4 characters from the end of the file
    $ext = substr("$var_website_image_name", - 4);
    
    // is the extension allowed
    if ($ext != '.jpg' || $ext != '.gif' || $ext != '.png')
    {
      return false;
    } else {
      return true;
    }
  }
?>

 

calling the function:

 

<?php
              // check its a valid image
              if (is_valid_image_file($var_website_image_name))
              {
                $errors[] = "The file you uploaded doesn't appear to be an image file.";
              }
?>

 

if i put ! infront of  if (is_valid_image_file($var_website_image_name))

 

it doesn't work the waqy i thought it would, could anyone explain the logic to me so i know for future reference lol

 

cheers

 

Graham

[GingerRobot]

I think the problem is that you are using 'or' in your if statement within your function, rather than 'and'. I assume you wanted to check to make sure the extension was one of those 3, in which case you need and.

 

If you think about your if statement, it will always be true.

 

You might find it easier to use an array and use the in_array() function, however.

[rhodesa]

<?php
  function is_valid_image_file($var_website_image_name)
  { 
    return in_array(
      substr($var_website_image_name,strrpos($var_website_image_name,'.')+1),
      array('jpg','gif','png')
    );
  }
?>

[graham23s]

Thanks guys,

 

that does seem a better way of doing things!

 

thanks again guys

 

Graham

[Jabop]

Rhodesa: that seems like a bad way to get the extension.

 

I prefer to use:

 

<?php

$img="blahblah.jpg";

$img=explode(".", $img);

$ext=array_pop($img);

?>

[GingerRobot]

I agree. The previous method relies on the the extension being just four letters.

[rhodesa]

Rhodesa: that seems like a bad way to get the extension.

 

I prefer to use:

 

<?php

$img="blahblah.jpg";

$img=explode(".", $img);

$ext=array_pop($img);

?>

 

both would work....why is this way any better?

[Jabop]

Simplicity and flexibility.

 

jpegs are still jpgs, but they have 4 chars. It's still a valid extension, shouldn't exclude it.

[rhodesa]

substr($var_website_image_name,strrpos($var_website_image_name,'.')+1)

 

get's everything AFTER the last period...regardless of length

[Jabop]

I was speaking of your array of allowed types, but that's beside the point. The method I posted is simpler in my opinion.

[rhodesa]

ah...i was just using the extensions they had originally posted...another good way to make sure it's an image (if you have gd enabled) is with:

 

<?php
  function valid_image($image_path){
    return (is_file($image_path) && @getimagesize($image_path));
  }
?>

[Jabop]

Another way to verify: http://us.php.net/manual/en/function.exif-imagetype.php

[br0ken]

substr($var_website_image_name,strrpos($var_website_image_name,'.')+1)

 

get's everything AFTER the last period...regardless of length

 

This would be the technique I'd used to extract the file extension. While you might argue both are just as easy this method requires one line of coding where as the other requires two.