if($ext == ('zip' || 'png')) { echo "Is it possible ?" }

Question

Hi all :)

I'm currently writing sort of a download manager and I was asking myself if that was possible:

if($ext == ('zip' || 'png')) { echo "Is it possible ?" }

It returns true everytime, so I guess it's not possible. But do you have an idea about how I could easily do this ? I mean, not with plenty of "if" or "switch"...

Thanks anyway ! :)

Answer 1

You can use regular expressions, e.g.

if(preg_match("/^(zip|png)$/", $ext) { echo “It is possible!” }

Related question: Checking for file-extensions in PHP with Regular expressions

Answer 2

You could go with a switch-case statement:

switch($ext)
{ 
  case 'png':
  case 'zip':
       // Will run for both 'png' and 'zip'
       echo "It is possible";
       break;
  default:
       echo "unknown extension!";
       break;
 }

Answer 3

if(($ext == 'zip') || ($ext == 'png')) { echo "It's possible." }

Answer 4

you could use in_array($ext,array('png','zip','another','more'))

see here: http://php.net/manual/en/function.in-array.php

Answer 5

if (in_array($ext, array('png', 'zip'))) {
    echo "Is it possible ?"
}

The array could be stored somewhere, if you need it multiple times.

Answer 6

if($ext == ('zip' || 'png')) is doing comparison in the following order -> ('zip' || 'png'), which because at least one is not null, returns TRUE. Substitute that in now, ($ext == TRUE), which I'm going to go out on a limb and guess that php is just evaluating this the same as it would ($ext), which is also true.

if ( $ext == 'zip' || $ext == 'png' ) will check what you are looking for.

Answer 7

It's definitely possible, but what you're doing there is incorrect code. Here is what you wrote:

if($ext == ('zip' || 'png')) { echo "Is it possible ?" }

And here is what that translates to in php:

if( (if $ext evaluates to true then return true) == ( if 'zip' evaluates to true then return true || if 'png' evaluates to true then return true ) )

So, since 'zip' isn't one of the 'empty' or 'false' values defined in php, and neither is 'png' you're basically running this if statement:

if($ext == true)

Which, if it isn't empty, it does.

What you want is - as previously mentioned:

if($ext == 'zip' || $ext == 'png')

Answer 8

Tiny advice: PHP uses similar to C boolean-type handling in a sense that actually any non-zero value is considered to be "true" in case of residing in conditional part of if- statement. for example if you would miss '=' symbol in compare construction and type if($var = "val") instead of if($var == "val") you will always get a true value in that statement, because '=' operator would return as a result of set-operation value from the right part "val" that is by-turn converted to 'true'. so it is better to write the literal in the left part of compare condition if("val" == $var) cause in this circumstance you would get an error if you loose one '=' symbol in '==' compare.

so your if-statement have to look like this: if('zip' == $ext || 'png' == $ext) { echo "Is it possible ?" }

also probably it would be better to put 'zip' and 'png' literals in constants with names FILE_TYPE_ZIP, FILE_TYPE_PNG or define some enumerated-entity like global PHP-array that resides at the top of your source-page or probably even create some separate class SupportedFileTypes in external file that would emphasize supported file types of your program (in that case check out http://stackoverflow.com/questions/254514/php-and-enums for details).

at the start of developing the question of performance doesn't have to bother you cause it is crucial to write code that is easy to read and evolve/optimize in future.