PHP中的If / Elseif语句

Question

We are trying to create an if/elseif statement for the variable $day . We defined the variable and its values in the HTML code associated with this PHP. I will paste the PHP section to this page. The problem is that the results page is only giving the response for "$day = 1". Does anyone know of an error in this code that would cause this to happen? We also tried using two equals signs but that made it worse!

echo "<p>";
                if ($day = 1) {
                    echo "Sunday Funday! What COMMITMENT to going out!";
                } elseif ($day = 2) {
                    echo "The start of what's sure to be a rough week. Drink away your sorrows.";
                } elseif ($day = 3) {
                    echo "Epic night! SO many themes at the bars!";
                } elseif ($day = 4) {
                    echo "Hump day!! But seriously, what are you doing...? Aren't you too hungover from last night?";
                } elseif ($day = 5) {
                    echo "Thirsty Thursday!! It's close enough to the weekend... right?";
                } elseif ($day = 6) {
                    echo "It's Friiiiiiday, Friiiiiiiday, Gotta get down on Friiiiiiiiiday!";
                } elseif ($day = 7) {
                    echo "It's FRATurday! Go have some fun!";

            } 

Answer 1

You are using assignment = when you mean to use comparison == .

Assignment evaluates to what is at the right hand side, so

if ($day = 1)

is the same as

if (1)

which due to these rules is the same as

if (true)

This should explain why the program behaves like it does and of course you now know how to fix it. But it would be even better if you used a switch statement:

switch($day) {
    case 1:
        echo "Sunday Funday! What COMMITMENT to going out!";
        break;
    case 2:
        echo "The start of what's sure to be a rough week.";
        break;
    // etc etc
}

Answer 2

Your are assigning ( = ). You need a logical equality ( == ).

if ($day == 1) {
  echo "Sunday Funday! What COMMITMENT to going out!";
}

Check out comparison and logical operators . Also the switch() statement .

Answer 3

If you have a long list of conditions to check against, you do not typically want to write a long chain of if / else statements. Rather try a switch block, or even an array map:

 $map = array(
    1 => "Sunday Funday! What COMMITMENT to going out!",
    2 => "The start of what's sure to be a rough week. Drink away your sorrows.",
    3 => "Epic night! SO many themes at the bars!",
    4 => "...",
 );

As then the code becomes pretty simple:

 echo $map[ $day ];

(Ideally would use an isset check. But for the development stage PHP is clever enough to give hints about missing entries. If the input values are already constrained/asserted, no need anyway.)

Answer 4

The comparison operator is == and not = .

Also try this lookup table approach, which is cleaner in this situation:

$day_msg = array(
    1 => "Sunday Funday! What COMMITMENT to going out!",
    2 => "The start of what's sure to be a rough week. Drink away your sorrows.",
    3 => "Epic night! SO many themes at the bars!",
    4 => "Hump day!! But seriously, what are you doing...? Aren't you too hungover from last night?",
    5 => "Thirsty Thursday!! It's close enough to the weekend... right?"
    6 => "It's Friiiiiiday, Friiiiiiiday, Gotta get down on Friiiiiiiiiday!",
    7 => "It's FRATurday! Go have some fun!"
);
echo "<p>";
echo $day_msg[$day];

Answer 5

you want to make all the conditions like this

            if ($day == 1) {
                echo "Sunday Funday! What COMMITMENT to going out!";
            } elseif ($day == 2) {
                echo "The start of what's sure to be a rough week. Drink away your sorrows.";
            } elseif ($day == 3) {
                echo "Epic night! SO many themes at the bars!";
            } elseif ($day == 4) {
                echo "Hump day!! But seriously, what are you doing...? Aren't you too hungover from last night?";
            } elseif ($day == 5) {
                echo "Thirsty Thursday!! It's close enough to the weekend... right?";
            } elseif ($day == 6) {
                echo "It's Friiiiiiday, Friiiiiiiday, Gotta get down on Friiiiiiiiiday!";
            } elseif ($day == 7) {
                echo "It's FRATurday! Go have some fun!";

        } 

Answer 6

您首先想到的是对的，您需要两个相等的符号。