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Closed 11 years ago.
Possible Duplicate:
what are the differences in die() and exit() in PHP?
I guess the main question is what is the difference between the 3 exactly?
What is the correct semantic usage for each one of these?
From what I see return false; can discontinue a function whereas die(); and exit(); will prevent any further code running at all.
Is this correct?
die() and exit() are precisely identical; they halt the entire PHP program and return to the OS. They're two different names for the same function.
return, on the other hand, ends a function call and returns to the caller. At the end of a program, return sets the status value that is returned to the OS; the program is going to exit no matter what.
According to docs PHP: exit Manual die() is an alias to exit() so they do the same function and that is to END the script.
The return statement ends a function and not the entire script, and returns the value that you choose.
Related
This question already has answers here:
Why is the semicolon optional in the last statement in php?
(3 answers)
Closed 6 years ago.
Today I have a little weird question.
Should I end my PHP script with exit or exit; and which is correct?.
Without ;
and
With ;
Thanks.
exit, exit;, exit(), and exit(); are exactly the same, but the fact is that you should not end your script with an exit() call, it's just bad practice (but it works).
EDIT
Clarifying why i said it's "bad practice", it's not about the functionality of "exit" itself, it's OK to halt the script execution if something bad happens, but the concept of "something bad" is really wide. In general, even if some unwanted condition occurs, the normal execution flow should reach to the end of the file. Just consider this example:
...some init stuff...
if (!user_is_authenticated) {
...print some nasty message...
exit();
}
...continue with normal stuff...
A better approach would be:
...some init stuff...
if (user_is_authenticated) {
...continue with normal stuff...
}
else {
...print some nasty message...
}
What's the difference? The difference is that in the second version you don't need to use exit(), which means if one day you need to do something after BOTH the "normal" and "unwanted" execution flows you can just add it at the end of the file.
It's more or less the same argument about why you should NOT use "return" in function bodies except at the end of the function..
It is allways a good practise to use semicolon
<?php
//exit program normally
exit;
exit();
exit(0);
//exit with an error code
exit(1);
exit(0376); //octal
?>
Like Johnny said, all those four forms of 'exit' statement work. Both exit and exit() work if there is no statements followed by any of these two language constructs. It doesn't work if there is any other PHP statements followed by these two constructs and semicolon's purpose is to end the statement to proceed to the next statement, therefore you need to use exit; or exit(); to avoid syntax error and also, in this case, without using semicolon is considered to be a bad practice in the coding conventions.
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Reference Guide: What does this symbol mean in PHP? (PHP Syntax)
(24 answers)
Closed 8 years ago.
Can you please explain to me the differences between two functions:
function &a(){
return something;
}
and
function b(){
return something;
}
Thanks!
The first returns a reference to something, the second a copy of something.
In first case, when the caller modify the returned value, something will be modified as a global variable do.
In the second case, modifying a copy as no effect to the source.
An ampersand before a function name means the function will return a reference to a variable instead of the value.
According to this LINK
Returning by reference is useful when you want to use a function to find to which
variable a reference should be bound. Do not use return-by-reference to increase
performance. The engine will automatically optimize this on its own. Only return
references when you have a valid technical reason to do so.
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Weird PHP error: 'Can't use function return value in write context'
(12 answers)
Closed 9 years ago.
This code:
if(!empty(trim($_POST['post']))){ }
return this error:
Fatal error: Can't use function return value in write context in ...
How can I resolve and avoid to do 2 checks ( trim and then empty ) ?
I want to check if POST is not only a blank space.
you cant use functions inside isset , empty statements. just assign the result of trim to a variable.
$r = trim($_POST['blop']);
if(!empty($r))....
edit: Prior to PHP 5.5
if (trim($_POST['post'])) {
Is functionally equivalent to what you appear to be trying to do. There's no need to call !empty
if (trim($_POST['post']) !== "") {
// this is the same
}
In the documentation it actually explains this problem specifically, then gives you an alternate solution. You can use
trim($name) == false.
In PHP, functions isset() and empty() are ment to test variables.
That means this
if(empty("someText")) { ... }
or this
if(isset(somefunction(args))) { ... }
doesn't make any sence, since result of a function is always defined, e.t.c.
These functions serve to tell wether a variable is defined or not, so argument must me a variable, or array with index, then it checks the index (works on objects too), like
if(!empty($_POST["mydata"])) {
//do something
} else {
echo "Wrong input";
}
This question already has answers here:
Closed 10 years ago.
Possible Duplicate:
The 3 different equals
Can anyone tell me why, when using the code below, I am getting redirected to elephant.com rather than seeing a 'giraffe!
<?php
$foo="giraffe";
if($foo="elephant"){
header("location:http://www.elephant.com");
exit();
}else{
echo $foo;}
?>
Thanks for looking
J
if($foo="elephant")
You're assigning $foo here, rather than comparing it; you should be doing:
if($foo=="elephant")
The result of an assignment operation is the value that's just been assigned; in this case, 'elephant' is evaluating to true.
Your if() statement has a single equal sign. This doesn't do a comparison in PHP; it sets the value and returns true.
In order to do a comparison, you need to use either a double-equal or a triple-equal sign:
if($foo == "elephant") { .... }
or
if($foo === "elephant") { .... }
The difference between the two is that double-equal doesn't care about the variable's data type, whereas triple-equal does. In this case, there's not much difference between them, but it's worth learning and understanding the differences because they can bite you if you don't know them. More info here: http://php.net/manual/en/language.operators.comparison.php
This question already has answers here:
Closed 11 years ago.
Possible Duplicate:
What is basic difference echo Vs print
The echo and print statements are nearly identical, but they have some differences.
For example, the print statement returns a value of 1 if it is successful
or a value of 0 if it is not successful, while the echo statement does
not return a value.
why print statement returns a value of 1 if it is successful. but echo doesn't. thank you
I've actually taken advantage of the return value of the print "function" in an ajax call:
return print json_encode($my_data);
It doesn't do anything at all with the return value, but it terminates the execution of the current script, which is a slightly prettier way of writing
echo json_encode($my_data);
die();
But as to why one returns something and the other doesn't.... probably isn't a terrible good reason for it. I reckon echo is ever so slightly (negligibly) faster because of it, whereas print has weird uses such as the aforementioned one.
As to what these other guys are saying about print() not being a language construct, but a function, I say to you, read the manual. It's a language construct too.