I have this code
$myvar = is_object($somevar) ? $somevar->value : is_array($somevar) ? $somevar['value'] : '';
issue is that sometime I am getting this error
PHP Error: Cannot use object of type \mypath\method as array in /var/www/htdocs/website/app/resources/tmp/cache/templates/template_view.html.php on line 988
line 988 is the above line I included. I am already checking if its object or array, so why this error then?
It has something to do with priority, or the way PHP is evaluating your expression. Grouping with parentheses solves the problem:
$myvar = is_object($somevar) ? $somevar->value : (is_array($somevar) ? $somevar['value'] : '');
See the notes here: http://www.php.net/manual/en/language.operators.comparison.php#language.operators.comparison.ternary
Note:
It is recommended that you avoid "stacking" ternary expressions. PHP's
behaviour when using more than one ternary operator within a single
statement is non-obvious:
Example #3 Non-obvious Ternary Behaviour
<?php
// on first glance, the following appears to output 'true'
echo (true?'true':false?'t':'f');
// however, the actual output of the above is 't'
// this is because ternary expressions are evaluated from left to right
// the following is a more obvious version of the same code as above
echo ((true ? 'true' : false) ? 't' : 'f');
// here, you can see that the first expression is evaluated to 'true', which
// in turn evaluates to (bool)true, thus returning the true branch of the
// second ternary expression.
?>
You need to place parenthesis around the second ternary:
$myvar = is_object($somevar) ? $somevar->value : (is_array($somevar) ? $somevar['value'] : '');
This must have something to do with operator precedence, though I'm not sure why yet.
Opinion: The ternary with or without parenthesis is difficult to read IMHO. I'd stick with the expanded form:
$myvar = '';
if(is_object($somevar)) {
$myvar = $somevar->value;
} elseif(is_array($somevar)) {
$myvar = $somevar['value'];
}
Related
This question already has answers here:
How to replace "if" statement with a ternary operator ( ? : )?
(16 answers)
Closed 3 years ago.
$n = isset($_GET["n"]) ? $_GET['n'] : '';
I find this "method" to avoid errors before insert stuff in the input type.. and it works.. but I would like a detailed explanation of this line. Thank you!
This is called the ternary operator shorthand of if...else
(condition) ? true : false
There is a condition which has been checked on left, if its true the statement after the ? will be execute else the statement after the : will execute.
It's called Ternary operator
The ternary operator is a shorthand for the if {} else {} structure. Instead of writing this:
if ($condition) {
$result = 'foo'
} else {
$result = 'bar'
}
You can write this:
$result = $condition ? 'foo' : 'bar';
If this $condition evaluates to true, the lefthand operand will be assigned to $result. If the condition evaluates to false, the righthand will be used.
In your case
If the value of $_GET["n"] isset then it'll take $_GET["n"] value.
if the value is not set then it'll take ('') value.
$n = isset($_GET["n"]) ? $_GET['n'] : '';
Simple question but it comes up all the time ... what is the best way to check variables in PHP. Looking for opinions / advice. In examples below assume $pricing could be not defined, correctly defined as 'price', or incorrectly defined as array(), etc..
//Method A ?
echo (!empty($pricing) && (string) $pricing == 'price' ? 'selected="true"' : '');
//Method B ?
echo (isset($pricing) && $pricing == 'price' ? 'selected="true"' : '');
// Method C ?
/// your idea ?
Method C: don't handle $pricing being undefined or of the wrong type in this expression.
By the time you reach this expression in your code, you should have already verified that the variable you're going to use exists and checked its type, and thrown an exception if it isn't what it's supposed to be, whether you do that explicitly or through a type declaration in a method.
By casting it to a string, or ignoring it if it doesn't exist, you may be covering up a potential problem that should cause an exception. If it's not a string, then something went wrong earlier in your code that you need to fix.
So just let your expression do one thing instead of multiple things.
echo $pricing == 'price' ? 'selected="true"' : '';
Then, if you see undefined variable notices in your error log, go back and fix the problem at the source (i.e. the place where $pricing was defined or should have been.)
If you're using PHP 7+, you have the null-coalesce operator (??) to compact the expression:
($pricing ?? '') === 'price' and print 'selected="true"';
Try it online at 3v4l.org.
Let's break that down:
($pricing ?? '') gracefully handles the scenario where $pricing has not been defined. If defined, this expression returns the defined value of $pricing: otherwise, it returns the empty string ''.
=== 'price' compares the now-defined value against exactly the value we are looking for. You can extend this test, of course. Like, if you had a set of defined values, you could instead use an in_array check.
and print 'selected="true"' reacts to the boolean result of the prior test, printing the desired value in the case of a match. Since outputting an empty string is equivalent to no output at all, we can simply use the and logical operator to conditionally output. Note that echo cannot be used here, as it's a language construct. Instead use print, printf, var_dump, etc.
That said, the emerging idiom for defaulting a potentially-undefined value uses the null-coalesce operator like:
$pricing = ($pricing ?? '');
I suggest defaulting in this way, versus the inline check given above, because it ensures $pricing is defined from that spot on. Said another way, don't litter your code with ($pricing ?? '') === 'price' checks: just do it once and be done with it.
As an aside, if you wanted to do multiple things on this condition, you could use an anonymous on-call:
($pricing ?? '') === 'price' and (function() {
echo 'this';
echo 'that';
})();
But I would not recommend these gymnastics.
I would write it this way:
echo (isset($pricing) && $pricing === 'price' ? 'selected="true"' : '');
This accomplishes the following:
condition evaluates to false if $pricing is undefined
condition evaluates to false if $pricing is not the same as 'price'
Finally, you are comparing with a specific value, anything other than that value will equate to false anyway, so checking for !empty() is redundant in this case.
Be sure to use the strict ( === ) comparison though, as if("some string" == 0) will return `true ( source ).
EDIT: Also, if you are unsure whether or not the variable has been defined (for example when working with $_POST), using isset() will save you a lot of trouble.
I want to evaluate a simple ternary operator inside of a string and can't seem to find the correct syntax.
My code looks like this:
foreach ($this->team_bumpbox as $index=>$member)
echo ".... class='{((1) ? abc : def)}'>....";
but I can't seem to get it to work properly. Any ideas on how to implement this?
You can't do it inside the string, per se. You need to dot-concatenate. Something like this:
echo ".... class='" . (1 ? "abc" : "def") . "'>....";
Well, you can do it actually:
$if = function($test, $true, $false)
{
return $test ? $true : $false;
};
echo "class='{$if(true, 'abc', 'def')}'";
I'll let you decide whether it is pure elegance or pure madness. However note that unlike the real conditional operator, both arguments to the function are always evaluated.
I am looking to expand on my PHP knowledge, and I came across something I am not sure what it is or how to even search for it. I am looking at php.net isset code, and I see isset($_GET['something']) ? $_GET['something'] : ''
I understand normal isset operations, such as if(isset($_GET['something']){ If something is exists, then it is set and we will do something } but I don't understand the ?, repeating the get again, the : or the ''. Can someone help break this down for me or at least point me in the right direction?
It's commonly referred to as 'shorthand' or the Ternary Operator.
$test = isset($_GET['something']) ? $_GET['something'] : '';
means
if(isset($_GET['something'])) {
$test = $_GET['something'];
} else {
$test = '';
}
To break it down:
$test = ... // assign variable
isset(...) // test
? ... // if test is true, do ... (equivalent to if)
: ... // otherwise... (equivalent to else)
Or...
// test --v
if(isset(...)) { // if test is true, do ... (equivalent to ?)
$test = // assign variable
} else { // otherwise... (equivalent to :)
In PHP 7 you can write it even shorter:
$age = $_GET['age'] ?? 27;
This means that the $age variable will be set to the age parameter if it is provided in the URL, or it will default to 27.
See all new features of PHP 7.
That's called a ternary operator and it's mainly used in place of an if-else statement.
In the example you gave it can be used to retrieve a value from an array given isset returns true
isset($_GET['something']) ? $_GET['something'] : ''
is equivalent to
if (isset($_GET['something'])) {
echo "Your error message!";
} else {
$test = $_GET['something'];
}
echo $test;
Of course it's not much use unless you assign it to something, and possibly even assign a default value for a user submitted value.
$username = isset($_GET['username']) ? $_GET['username'] : 'anonymous'
You have encountered the ternary operator. It's purpose is that of a basic if-else statement. The following pieces of code do the same thing.
Ternary:
$something = isset($_GET['something']) ? $_GET['something'] : "failed";
If-else:
if (isset($_GET['something'])) {
$something = $_GET['something'];
} else {
$something = "failed";
}
It is called the ternary operator. It is shorthand for an if-else block. See here for an example http://www.php.net/manual/en/language.operators.comparison.php#language.operators.comparison.ternary
? is called Ternary (conditional) operator : example
What you're looking at is called a Ternary Operator, and you can find the PHP implementation here. It's an if else statement.
if (isset($_GET['something']) == true) {
thing = isset($_GET['something']);
} else {
thing = "";
}
If you want an empty string default then a preferred way is one of these (depending on your need):
$str_value = strval($_GET['something']);
$trimmed_value = trim($_GET['something']);
$int_value = intval($_GET['somenumber']);
If the url parameter something doesn't exist in the url then $_GET['something'] will return null
strval($_GET['something']) -> strval(null) -> ""
and your variable $value is set to an empty string.
trim() might be prefered over strval() depending on code (e.g. a Name parameter might want to use it)
intval() if only numeric values are expected and the default is zero. intval(null) -> 0
Cases to consider:
...&something=value1&key2=value2 (typical)
...&key2=value2 (parameter missing from url $_GET will return null for it)
...&something=+++&key2=value (parameter is " ")
Why this is a preferred approach:
It fits neatly on one line and is clear what's going on.
It's readable than $value = isset($_GET['something']) ? $_GET['something'] : '';
Lower risk of copy/paste mistake or a typo: $value=isset($_GET['something'])?$_GET['somthing']:'';
It's compatible with older and newer php.
Update
Strict mode may require something like this:
$str_value = strval(#$_GET['something']);
$trimmed_value = trim(#$_GET['something']);
$int_value = intval(#$_GET['somenumber']);
This below does not seem to work how I would expect it, event though $_GET['friendid'] = 55 it is returning NULL
<?PHP
$_GET['friendid'] = 55;
$friendid = (!isset($_GET['friendid'])) ? $_GET['friendid'] : 'empty';
echo $friendid;
exit;
?>
As of PHP 7's release, you can use the null-coalescing operator (double "?") for this:
$var = $array["key"] ?? "default-value";
// which is synonymous to:
$var = isset($array["key"]) ? $array["key"] : "default-value";
In PHP 5.3+, if all you are checking on is a "truthy" value, you can use the "Elvis operator" (note that this does not check isset).
$var = $value ?: "default-value";
// which is synonymous to:
$var = $value ? $value : "default-value";
Remove the !. You don't want to negate the expression.
$friendid = isset($_GET['friendid']) ? $_GET['friendid'] : 'empty';
If you're lazy and risky, you can use error control operator # and short form of ternary operator.
$friendid = #$_GET['friendid']?: 'empty';
Currently you're working with the ternary operator:
$friendid = (!isset($_GET['friendid'])) ? $_GET['friendid'] : 'empty';
Break it down to an if-else statement and it looks like this:
if(!isset($_GET['friendid']))
$friendid = $_GET['friendid'];
else
$friendid = 'empty';
Look at what's really happening in the if statement:
!isset($_GET['friendid'])
Note the exclamation mark (!) in front of the isset function. It's another way to say, "the opposite of". What you're doing here is checking that there is no value already set in $_GET['friendid']. And if so, $friendid should take on that value.
But really, it would break since $_GET['friendid'] doesn't even exist. And you can't take the value of something that isn't there.
Taking it from the start, you have set a value for $_GET['friendid'], so that first if condition is now false and passes it on to the else option.
In this case, set the value of the $friendid variable to empty.
What you want is to remove the exclamation and then the value of $friendid will take on the value of $_GET['friendid'] if it has been previously set.
The best solution for this question, i.e. if you also need to 'check for the empty string', is empty().
$friendid = empty($_GET['friendid']) ? 'empty' : $_GET['friendid'];
empty() not only checks whether the variable is set, but additionally returns false if it is fed anything that could be considered 'empty', such as an empty string, empty array, the integer 0, boolean false, ...
I am using Null coalescing operator operator in if condition like this
if($myArr['user'] ?? false){
Which is equivalent to
if(isset($myArr['user']) && $myArr['user']){
From your reply to Philippe I think you need to have a look at the differences between empty and isset.
To summarise, isset() will return boolean TRUE if the variable exists. Hence, if you were to do
$fid = $_GET['friendid'] = "";
$exists = isset($fid);
$exists will be TRUE as $_GET['friendid'] exists. If this is not what you want I suggest you look into empty. Empty will return TRUE on the empty string (""), which seems to be what you are expecting. If you do use empty, please refer to the documentation I linked to, there are other cases where empty will return true where you may not expect it, these cases are explicitly documented at the above link.
if friendid is NOT set, friendid = friendid otherwise friendid = empty
Okay, I may have been having a similar issue not being familiar with the ! situation as jasondavis had.
Kind of confusing but finding out not having the ! as in... isset($avar) compared to !isset($avar) can make quite the difference.
So with the ! in place, is more stating a YES as in
since $_GET['friendid'] = 55; has been initialized...
tell me 'no' - the opposite - that it hasn't and set it to empty.
$friendid = (!isset($_GET['friendid'])) ? $_GET['friendid'] : 'empty';
where not having the ! tells me yes it has something in it, leave it be.
$friendid = (!isset($_GET['friendid'])) ? $_GET['friendid'] : 'empty';
Was far less confusing with if A$="" then.... work it. ( or if $A="" for those of PHP ).
I find this use of strings and variables all as strings to be very daunting at times. Even through the confusion, I can actually understand why... just makes things a tad difficult to grasp for me.
For me, if I need to know BOTH are true
key is set
value is truthy
and if not, use another result:
the shortest way is
$result = ($arr['b'] ?? 0) ?: $arr['a'];
(ie. if b is_set AND has a real value, use it. Otherwise use a)
So in this scenario:
$arr = ['a' => 'aaa', 'b' => 'bbb'];
$result = 'aaa'