你看到这个破裂吗？ 任何问题？ 简单的php if elseif语句

I'm a total PHP newb, so there is probably a better way of outputting a row's class based on different variables.

Is this bad, and if it is why is it?

    if ($variable1 > 0 && $variable2 != 2)  {
        echo "<tr class='variable1'>";
        }
        elseif ($variable2==2)
        {
         echo "<tr class='variable2'>";
        }
        else {
              echo "<tr>";
                 }

I would write it like this:

$class_name = '';
if (2 == $variable2)
{
    $class_name = 'variable2';
}
elseif ($variable1 > 0)
{
    $class_name = 'variable1';
}
echo '<tr class="' , $class_name , '">';

notice that on the equality test I use the constant before the variable.. this is a habit so that if I miss one equal it would result in an error that I would be forced to correct it instead of a "strange" behavior

another thing is that I give the initial value to $class_name and that will be the default one

also I use apostrophes instead of quotation marks because it is faster (because the way you did it php will parse the string for variables)

and the last thing is that I echo multiple string.. that's also faster than concatenating 3 strings (

echo '<tr class="' , $class_name , '">'; 

and not echo

'<tr class="' . $class_name . '">';

)

Well you could start with

if ($variable2==2)

which would safe you the $variable2 != 2 if you continue with

elseif ($variable1 > 0)

but generally I see no mistake. Of course this depends on what else you want to do.

You could put the if ($variable2==2) first and then you wouldn't need to negate it on the other if statement. Like this:

if ($variable2==2){
    echo '<tr class="variable1">';
}elseif ($variable1 > 0)  {
    echo '<tr class="variable2">';
}else {
    echo '<tr>';
}

Looks okay to me though, but it depends on the rest of the code really, you might be able to change the code slightly to make it easier to read but it looks pretty simple so, if it works, i'd keep it how it is.

The php code is syntactically correct, although the indentation seems to be messed up. The outputted HTML code is invalid though, since attributes values must be enclosed in double, not single quotes.

I'd also suggest a slight reordering:

if ($variable2 == 2) {
    echo '<tr class="variable2">';
} elseif ($variable1 > 0)  {
    echo '<tr class="variable1">';
} else {
    echo '<tr>';
}

echo ( ( $variable1 > 0 ) && ( $variable2 != 2 ) )
    ? "<tr class='variable1'>"
    : ( $variable2 == 2 )
        ? "<tr class='variable2'>"
        : "<tr>";

2 rules for you to learn how to program:

.1. DRY: Don't Repeat yourself.

if you have your tr tag typed 3 times, you can say for sure that's wrong.

.2. Separate business logic from presentation logic. Use templates for output. Prepare your data first and start output only if everything is ready.

So, first you have to define your variables

if ($variable2 == 2){
    $class = "variable1";
}elseif ($variable1 > 0)  {
    $class = "variable2";
}else {
    $class = "";
}

next you have to include a template and write native HTML in it, with as little PHP as possible:

<tr class="<?=$class?>">

Well, that is a really unfortunate approach at many levels, but I can tell you that even I started writing code the way you describe, only that was over 12 years ago.

I can also tell you that eventually mixing php with markup in the same files will come to bite you in the rear, and sooner than you think. As with most things in life, getting it done faster and worrying about the rest later is a bad approch when developing in PHP.

A few pointers:

• Try VERY hard to not mix PHP and HTML or other markup in the same file. Doing this will be more work when first developing but a LOT less work when changing and maintaining your code later.
• PHP is an Object-oriented language. Learn how to use that to your advantage. Create libaries of your own classes for later reuse.
• Use a good editor/IDE like NetBeans or Komode Editor - which are free.
• The best resource for PHP info is the online PHP manual. Not only the manual pages are great, but the code snippets users contribute are full of little gems - and some glaring n00b errors too, but you will learn to filter that.
• If you are new to programming in general, PLEASE do yourself a favor and get a book on programming. PHP is a very forgiving language and lets you get away with a lot of bad practices. As I said, those will come back sooner or later to get you.
• After you gain some experience consider using a PHP framework, like CodeIgniter, CakePHP or ZendFramework. Try a few of them and choose the one that works for you.
• Don't listen to people that tell you that PHP sucks. PHP is the most powerful programming language I have used, maybe excepting C and Prolog. The PHP array is the most powerful data structure I have encountered in any language - except linked lists in C ;-)
• You CAN use PHP for every kind of programming task, including Windows and Linux server applications and full desktop graphical applications too. In fact, in my experience, PHP is faster than any dynamic language I have benchmarked it against - python, perl, ruby , tcl are all slower performing than PHP. But don't take my word for it, try it yourself :-)

A couple of links:

30+ PHP best practices for beginners

PHP bad programming practices

PHP OOP in full effect

PHP manual