条件语句中的PHP“或”运算符 - newb问题！

Question

Forgive me if this has been covered before, I searched to no avail.

I have a script that looks into a directory to find the files inside. There is a conditional line that only looks for files with a certain extension:

if(strtolower(substr($file, -3)) == "mp4"){...

So that will only look for files with an 'mp4' extension.

I need to add some "or" operators to add two more extension types. I tried the following but it didn't work:

if(strtolower(substr($file, -3)) == "mp4" || == "mov" || == "flv"){...

Now the line seems to be ignored and it gets every file in the directory. If anyone could help me out, I'd be very grateful! I know this is probably as basic as it gets, but my grasp of PHP is extremely limited (although I do see its beauty!!!)

Thanks in advance.

Answer 1

The way you tried it does not work because the comparison operator == is a binary operator and expects two operands, ie operand1 == operand2 . The same applies to the logical OR operator that is also a binary operator, ie operand1 || operand2 operand1 || operand2 .

That means you would need to write something like this:

$ext = strtolower(substr($file, -3));
if ($ext == "mp4" || $ext == "mov" || $ext == "flv")

Here $ext is just used to avoid repeated call of strtolower(substr($file, -3)) . In this case each binary operator has two operands:

((($ext == "mp4") || ($ext == "mov")) || ($ext == "flv"))
   \__/    \___/
     \__==___/        \__/    \___/
         \              \__==___/
          \_______||_______/
                   \                      \__/    \___/
                    \                       \__==___/
                     \________________||_______/

( I added parentheses to highlight the order in which the expression is evaluated. )

So this is how you would have to write it.

But you could also use an array and in_array :

in_array(strtolower(substr($file, -3)), array("mp4","mov","flv"))

And pathinfo is probably better to get the file name extension, so:

in_array(pathinfo($file, PATHINFO_EXTENSION), array("mp4","mov","flv"))

Answer 2

The problem is that PHP does not automatically know that you want to compare to strtolower(substr($file, -3)) in each "or" section. You need to explicitly state this:

if(strtolower(substr($file, -3)) == "mp4" || strtolower(substr($file, -3)) == "mov" || strtolower(substr($file, -3)) == "flv"){...

Note that it would probably be neater to do something like:

$tmp = strtolower(substr($file, -3));

if($tmp == "mp4" || $tmp == "mov" || $tmp == "flv"){...

Answer 3

 $ext = strtolower(substr($file, -3));

 if($ext == "mp4" || $ext == "mov" || $ext == "flv"){...

Answer 4

Another way to do it :

if ( in_array(strtolower(substr($file, -3))),  array('mp4', 'mov', 'flv') ) {
    // do something
}

Answer 5

更简洁的方式：

if ( preg_match('/(mp4|mov|flv)$/', $file) ) { ...

Answer 6

If you want to match only specific filenames in a directory, you can use glob

$files = glob('/path/to/dir/*.{mp4,mov,flv}', GLOB_BRACE);

to return an array of matching file paths.

Or you use fnmatch to match a filename against a pattern.

In addition, if you want to make sure the images are really images, consider checking against the MimeType instead of or in addition to the extension

Answer 7

if you want to compare using || , here's the syntax:

if(strtolower(substr($file, -3)) == "mp4" || strtolower(substr($file, -3)) == "mov" || strtolower(substr($file, -3)) == "flv"){...

of course to make it a bit faster, fill strtolower(substr($file, -3)) in a variable so php doesn't execute those functions more than once:

$extension=strtolower(substr($file, -3));
if($extension == "mp4" || $extension == "mov" || $extension == "flv"){...

The other good news is, PHP got a builtin function to search whether a value exists in an array of values ( in_array ):

if(in_array(strtolower(substr($file, -3)), array('mp4', 'mov', 'flv')))

One last thing, if you have simple strings like those, ones who you don't want php to expand variables and stuff inside, use single qutations instead of doubles , that is a good practice and saves some execution time (of course barely noticed with a string or two, but it's a good practice on the long range).

Answer 8

$ext = strtolower(substr($file, -3));

switch ( $ext ) { case 'mp4': case 'mov': case 'flv': /// some operation break; }