PHP语法用？ 并且：[重复]

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What is the PHP ? : operator called and what does it do?

I found the answer to something I was looking for, but I don't quite understand the syntax because they used, I think, short tags. Here is the code:

$temp = is_array($value) ? $value : trim($value);

Could someone explain how this works? I think this means if true, return the value and if false return the value trimmed, but I'm not sure. Can there be more than two options, or is it strictly true and false?

You are correct. This is a conditional operator, ?: is a ternary operator.

<?php

// Example usage for: Ternary Operator
$temp = is_array($value) ? $value : trim($value);

// The above is identical to this if/else statement
if (is_array($value)) {
    $temp = $value;
} else {
    $temp = trim($value);
}

?>

Take a look half way down this page for more information:

http://php.net/manual/en/language.operators.comparison.php

It is equivalent to

if (is_array($value)){
    $temp = $value;
}
else{
    $temp = trim($value);
}

More info: http://en.wikipedia.org/wiki/Ternary_operation

It's basically the same as

if(is_array($value)) {
   $temp = $value;
} else {
   $temp = trim($value);
}

$condition ? true : false, the ? instruction is same as

if($condition)
   true
else 
   false

so in your example the code is same as

if(is_array($value))
  $temp = $value
else 
  $temp = trim($value);

You are correct. If is_array($value) returns true then the expression sets $temp = $value otherwise $temp = trim($value).

Strictly two choices. You interpreted it correctly.

if (is_array($value)) $temp = $value;
else $temp = trim($value);

If you wanted to hack this syntax to have 3 values you could do $temp = (condition1) ? true : (condition2) ? true2 : false;

This is ternary operator. Its will convert exp before ? to a bool. If you want more option just combine multi ?:.

(con?trueorfalseiftrue:otherwise)? (con2?_:_):(con3?_:_)