How do I convert the value of a PHP variable to string?
I was looking for something better than concatenating with an empty string:
$myText = $myVar . '';
Like the ToString() method in Java or .NET.
You can use the casting operators:
$myText = (string)$myVar;
There are more details for string casting and conversion in the Strings section of the PHP manual, including special handling for booleans and nulls.
This is done with typecasting:
$strvar = (string) $var; // Casts to string
echo $var; // Will cast to string implicitly
var_dump($var); // Will show the true type of the variable
In a class you can define what is output by using the magical method __toString. An example is below:
class Bottles {
public function __toString()
{
return 'Ninety nine green bottles';
}
}
$ex = new Bottles;
var_dump($ex, (string) $ex);
// Returns: instance of Bottles and "Ninety nine green bottles"
Some more type casting examples:
$i = 1;
// int 1
var_dump((int) $i);
// bool true
var_dump((bool) $i);
// string "1"
var_dump((string) 1);
Use print_r:
$myText = print_r($myVar,true);
You can also use it like:
$myText = print_r($myVar,true)."foo bar";
This will set $myText to a string, like:
array (
0 => '11',
)foo bar
Use var_export to get a little bit more info (with types of variable,...):
$myText = var_export($myVar,true);
You can either use typecasting:
$var = (string)$varname;
or StringValue:
$var = strval($varname);
or SetType:
$success = settype($varname, 'string');
// $varname itself becomes a string
They all work for the same thing in terms of Type-Juggling.
How do I convert the value of a PHP
variable to string?
A value can be converted to a string using the (string) cast or the strval() function. (Edit: As Thomas also stated).
It also should be automatically casted for you when you use it as a string.
You are looking for strval:
string strval ( mixed $var )
Get the string value of a variable.
See the documentation on string for
more information on converting to
string.
This function performs no formatting
on the returned value. If you are
looking for a way to format a numeric
value as a string, please see
sprintf() or number_format().
For primitives just use (string)$var or print this variable straight away. PHP is dynamically typed language and variable will be casted to string on the fly.
If you want to convert objects to strings you will need to define __toString() method that returns string. This method is forbidden to throw exceptions.
Putting it in double quotes should work:
$myText = "$myVar";
I think it is worth mentioning that you can catch any output (like print_r, var_dump) in a variable by using output buffering:
<?php
ob_start();
var_dump($someVar);
$result = ob_get_clean();
?>
Thanks to:
How can I capture the result of var_dump to a string?
Another option is to use the built in settype function:
<?php
$foo = "5bar"; // string
$bar = true; // boolean
settype($foo, "integer"); // $foo is now 5 (integer)
settype($bar, "string"); // $bar is now "1" (string)
?>
This actually performs a conversion on the variable unlike typecasting and allows you to have a general way of converting to multiple types.
In addition to the answer given by Thomas G. Mayfield:
If you follow the link to the string casting manual, there is a special case which is quite important to understand:
(string) cast is preferable especially if your variable $a is an object, because PHP will follow the casting protocol according to its object model by calling __toString() magic method (if such is defined in the class of which $a is instantiated from).
PHP does something similar to
function castToString($instance)
{
if (is_object($instance) && method_exists($instance, '__toString')) {
return call_user_func_array(array($instance, '__toString'));
}
}
The (string) casting operation is a recommended technique for PHP5+ programming making code more Object-Oriented. IMO this is a nice example of design similarity (difference) to other OOP languages like Java/C#/etc., i.e. in its own special PHP way (whenever it's for the good or for the worth).
As others have mentioned, objects need a __toString method to be cast to a string. An object that doesn't define that method can still produce a string representation using the spl_object_hash function.
This function returns a unique identifier for the object. This id can be used as a hash key for storing objects, or for identifying an object, as long as the object is not destroyed. Once the object is destroyed, its hash may be reused for other objects.
I have a base Object class with a __toString method that defaults to calling md5(spl_object_hash($this)) to make the output clearly unique, since the output from spl_object_hash can look very similar between objects.
This is particularly helpful for debugging code where a variable initializes as an Object and later in the code it is suspected to have changed to a different Object. Simply echoing the variables to the log can reveal the change from the object hash (or not).
I think this question is a bit misleading since,
toString() in Java isn't just a way to cast something to a String. That is what casting via (string) does, and it works as well in PHP.
// Java
String myText = (string) myVar;
// PHP
$myText = (string) $myVar;
Note that this can be problematic as Java is type-safe (see here for more details).
But as I said, this is casting and therefore not the equivalent of Java's toString().
toString in Java doesn't just cast an object to a String. It instead will give you the String representation. And that's what __toString() in PHP does.
// Java
class SomeClass{
public String toString(){
return "some string representation";
}
}
// PHP
class SomeClass{
public function __toString()
{
return "some string representation";
}
}
And from the other side:
// Java
new SomeClass().toString(); // "Some string representation"
// PHP
strval(new SomeClass); // "Some string representation"
What do I mean by "giving the String representation"?
Imagine a class for a library with millions of books.
Casting that class to a String would (by default) convert the data, here all books, into a string so the String would be very long and most of the time not very useful.
To String instead will give you the String representation, i.e., only the library's name. This is shorter and therefore gives you less, but more important information.
These are both valid approaches but with very different goals, neither is a perfect solution for every case, and you have to choose wisely which fits your needs better.
Sure, there are even more options:
$no = 421337 // A number in PHP
$str = "$no"; // In PHP, the stuff inside "" is calculated and variables are replaced
$str = print_r($no, true); // Same as String.format();
$str = settype($no, 'string'); // Sets $no to the String Type
$str = strval($no); // Get the string value of $no
$str = $no . ''; // As you said concatenate an empty string works too
All of these methods will return a String, some of them using __toString internally and some others will fail on Objects. Take a look at the PHP documentation for more details.
Some, if not all, of the methods in the previous answers fail when the intended string variable has a leading zero, for example, 077543.
An attempt to convert such a variable fails to get the intended string, because the variable is converted to base 8 (octal).
All these will make $str have a value of 32611:
$no = 077543
$str = (string)$no;
$str = "$no";
$str = print_r($no,true);
$str = strval($no);
$str = settype($no, "integer");
The documentation says that you can also do:
$str = "$foo";
It's the same as cast, but I think it looks prettier.
Source:
Russian
English
Double quotes should work too... it should create a string, then it should APPEND/INSERT the casted STRING value of $myVar in between 2 empty strings.
You can always create a method named .ToString($in) that returns
$in . '';
If you're converting anything other than simple types like integers or booleans, you'd need to write your own function/method for the type that you're trying to convert, otherwise PHP will just print the type (such as array, GoogleSniffer, or Bidet).
PHP is dynamically typed, so like Chris Fournier said, "If you use it like a string it becomes a string". If you're looking for more control over the format of the string then printf is your answer.
You can also use the var_export PHP function.
$parent_category_name = "new clothes & shoes";
// To make it to string option one
$parent_category = strval($parent_category_name);
// Or make it a string by concatenating it with 'new clothes & shoes'
// It is useful for database queries
$parent_category = "'" . strval($parent_category_name) . "'";
For objects, you may not be able to use the cast operator. Instead, I use the json_encode() method.
For example, the following will output contents to the error log:
error_log(json_encode($args));
Try this little strange, but working, approach to convert the textual part of stdClass to string type:
$my_std_obj_result = $SomeResponse->return->data; // Specific to object/implementation
$my_string_result = implode ((array)$my_std_obj_result); // Do conversion
__toString method or (string) cast
$string=(string)$variable; //force make string
you can treat an object as a string
class Foo
{
public function __toString()
{
return "foo";
}
}
echo new Foo(); //foo
also, have another trick, ı assume ı have int variable ı want to make string it
$string=''.$intvariable;
This can be difficult in PHP because of the way data types are handled internally. Assuming that you don't mean complex types such as objects or resources, generic casting to strings may still result in incorrect conversion. In some cases pack/unpack may even be required, and then you still have the possibility of problems with string encoding. I know this might sound like a stretch but these are the type of cases where standard type juggling such as $myText = $my_var .''; and $myText = (string)$my_var; (and similar) may not work. Otherwise I would suggest a generic cast, or using serialize() or json_encode(), but again it depends on what you plan on doing with the string.
The primary difference is that Java and .NET have better facilities with handling binary data and primitive types, and converting to/from specific types and then to string from there, even if a specific case is abstracted away from the user. It's a different story with PHP where even handling hex can leave you scratching your head until you get the hang of it.
I can't think of a better way to answer this which is comparable to Java/.NET where _toString() and such methods are usually implemented in a way that's specific to the object or data type. In that way the magic methods __toString() and __serialize()/__unserialize() may be the best comparison.
Also keep in mind that PHP doesn't have the same concepts of primitive data types. In essence every data type in PHP can be considered an object, and their internal handlers try to make them somewhat universal, even if it means loosing accuracy such as when converting a float to int. You can't deal with types as you can in Java unless your working with their zvals within a native extension.
While PHP userspace doesn't define int, char, bool, or float as an objects, everything is stored in a zval structure which is as close to an object that you can find in C, with generic functions for handling the data within the zval. Every possible way to access data within PHP goes down to the zval structure and the way the zend vm allows you to handles them without converting them to native types and structures. With Java types you have finer grained access to their data and more ways to to manipulate them, but also greater complexity, hence the strong type vs weak type argument.
These links my be helpful:
https://www.php.net/manual/en/language.types.type-juggling.php
https://www.php.net/manual/en/language.oop5.magic.php
I use variableToString. It handles every PHP type and is flexible (you can extend it if you want).
Related
why this is not possible:
$user = (User) $u[0];
but this is possible
$bool = (boolean) $res['success'];
I use PHP 7.0.
As I know, in PHP you can only cast to some types:
(int), (integer) - cast to integer
(bool), (boolean) - cast to boolean
(float), (double), (real) - cast to float (real deprecated in PHP 8.0)
(string) - cast to string
(binary) - cast to binary string (PHP 6)
(array) - cast to array
(object) - cast to object
(unset) - cast to NULL (PHP 5) (depracted in PHP 7.2) (removed in 8.0)
(see Type Casting)
Instead you could use instanceof to check of specific type:
if($yourvar instanceof YourClass) {
//DO something
} else {
throw new Exception('Var is not of type YourClass');
}
EDIT
As mentioned by Szabolcs Páll in his answer, it is also possible to declare a return type or parameter type, but in that cases an exception (TypeError) will be throwen, if the type does not match.
function test(): string
{
return 'test';
}
function test(string $test){
return "test" . $test;
}
Since PHP 7.2 it is also possible to make the types nullable by adding ? in front of them:
function test(): ?string
{
return null;
}
You can use PHPDoc
/** #var User $user */
$user = $u[0];
If you just want to ensure a variable is instance of YourClass and let exception handling to the typesystem you can use the following function:
function implicitFakeCast($myClass): YourClass
{
return $myClass;
}
Note: this will not actually do any casting, rather it throws exceptions in case of class mismatch and lets intellisense treat it as an instance of the target class.
For people that do want to be able to cast to a class type. I've found a gist by #borzilleri that uses serialize and unserialize to achieve this: https://gist.github.com/borzilleri/960035.
TL;DR:
// make sure to include the namespace when casting
$className = "Some\\NameSpace\\SomeClassName";
$classNameLength = strlen( $className );
$castedItem = unserialize(
preg_replace(
'/^O:\d+:"[^"]++"/',
"O:$classNameLength:\"$className\"",
serialize( $item )
)
)
It's really simple in php8:
$item = (fn($item):YourClass=>$item)($item);
Objects and primitive types are different. Since it's called as primitive types, they are really simple, maybe only 1 byte, 2 bytes, or 4 bytes, and at most 8 bytes.
When we are talking about object, this object can have different attributes with the others. Then the question from PHP will be is, "is this object really from my Class?" "How to convert this object to my Class?". Thus, you can't parse right away the object using
$myObject = (ClassName) $variable
Then how to cast it? Dunno, but usually the approach is like this:
Create constructor for the class
In the class, make a method that specifically accept certain parameters, maybe array
here is sample:
public class MyAwesomeClass{
function __construct($thisIsArray){
$this->attributeA = $thisIsArray["A"];
$this->attributeB = $thisIsArray["B"];
......
}
static function fromArray($thisIsArray){
return MyAwesomeClass($thisIsArray);
}
}
$obj = MyAwesomeClass::fromArray($attributes);
In addition to the answer on why this is not possible, I would suggest that you write a builder function that creates an object, based on your input. so it would look something like
$user = User::buildFromSomeArrayInput($u[0]);
And then have a builder create a new User object, assign the right properties, etc. You could just do all this in-place of course, but having a builder function makes sure you won't be doing this on several locations, AND you can set private properties as it is a class-member function. It is a bit more work then having it magically work, but not that much.
The only issue you might have is when you do have a different object that does not expose all the internals you might need. But this is for a reason, as internals might change -> you don't want to rely on that.
There are hacks out there that suggest doing this with serialization. I would suggest to steer away from them, as they are hackish and as far as i'm concerned, not very clear.
I have been doing some research online and it appears that the answer to my question is no, but I realize there are times when I might miss something or search for something incorrectly. I know in languages like C++, when a variable is declared it can be declared as int or string. Is it possible to force this in PHP?
For Example:
<?php
(int)$var = 5;
?>
will be validated and not cause an error in PHP, but:
<?php
$var = 5;
?>
will cause an error because it was not cast as a type string, int, object, etc...
I know PHP is loosely typed so this may not be an option, however I would like to use it that way I ensure that I sanitize data appropriately and improve readability by letting others know exactly what is going on with the code. I am hoping there is a way to enforce this in the php.ini file or to load it in a script that will always be executed by my program.
Thank you for any help you can offer!
PHP is loosely typed and does not require you to declare a variable type when declaring a variable. You can’t change that behavior with a magic php.ini directive.
The benefit of having “loose typing” is that it allows for flexibility. It allows you to create dynamic applications without having to worry about the type of the variable – PHP makes this possible by not enforcing variable types.
However, if you must convert a variable into a particular format, just cast it:
$int = (int) $foo;
$str = (string) $foo;
$bool = (bool) $foo;
$float = (float) $foo;
...
There are functions to do the same, e.g. intval(), strval(), boolval() – all of them do the same task, but a function is very useful when you want to use it as a callback to another function.
Today i very much wondered, that if the string contain first letter has integer you can add that value into another integer variable.
$a = 20;
$b = "5doller";
$a+=$b;
echo $a;
Will any one can explain how this is happen and if i have like string like "dollar5" it wont add.
PHP is not strongly typed.
since the first character of your string is an integer and you are using the + operator it interprets the 5dollar as int and returns 25
example: http://en.wikipedia.org/wiki/Strong_typing#Example
PHP has a type conversion philosofy, that will auto convert the type of the data on runtime depending on the context. This may have it's advantages and disadvantages, and there are people against it and people who think it's ok (like in almost everything in life).
For more info about its behaviour please have a look on the php documentation: http://www.php.net/manual/en/language.types.type-juggling.php
It will try to see the string as an integer to ease your life if you use the arithmetic operator "+"(detecting the first character "5"), but leading to strange behaviours if not done properly.
That doesn't mean it doesn't have a type, $b is actually a string, only that it tries to convert it on runtime, but $b will still remain as a string.
To check this and/or prevent the strange behaviours you could use the php native functions to check the types:
$a = 20;
$b = "5doller";
if(is_integer($b)){
$a+=$b;
} elseif (is_string($b)) {
$a.=$b;
}
echo $a;
Or you can use gettype() which will return the variable type, and do a switch case or whatever you like to it. But in my opinion it would be over-coding, just use your common sense and be careful and normally it will be ok.
I would like or I will prefer indicate the real type of a parameter in a function with Php, it's possible ?
Example :
<?php
function test($param)
{
echo $param;
}
$str = "hiiiii everyone";
test($str);
?>
Instead of put just $param in the function test; I would like put something like that
function test(string $param) // string is the type of the param, that can be int, long ect or an object which I had created.
It's possible to do that with the last version of PHP ?
What you are looking for is Type Hinting. However, as stated in the linked manual page:
Type hints can not be used with scalar types such as int or string.
This means that no, you cannot force the argument for a function to be string. You can force it to be an instance of a specific class, something which is callable, or an array.
If you want to force an argument to be a string, do something like this:
function my_func ($mustBeAString) {
if (!is_string($mustBeAString)) return;
// Do stuff here
}
No. PHP is a dynamically typed language; variables (and as such, parameters) don't have set types. You could try and enforce your own thing using gettype, ie:
function test($param) {
if(gettype($param) != "string")
throw new TypeException //or something
}
But it's a bad idea. Don't try and implement features from other languages in a language you're new to. Just try and embrace the proper way and see how it goes from there.
Type Hinting was introduced in PHP5. You can now force parameters to be of a certain type by providing that type in the parameter list itself, as your example demonstrated.
Unfortunately, scalar objects (like int, and string) are not permitted.
You can do your own checking internally to determine whether the passed object is of the proper type using methods like gettype(), is_string() (handle other types as well), or even the type operator instanceof.
I would like to bring this to the table:
var_dump($str);
Hai. I was making this simple string class and was wondering if there was a more natural way of doing it.
class Str{
function __construct($str){
$this->value = $str;
$this->length = strlen($str);
..
}
function __toString(){
return $this->value;
}
..
}
so now i have to use it like this:
$str = new Str('hello kitty');
echo $str;
But that doesnt look very 'natural' with the parentheses. So i was wondering if something like this, or similar was possible.
$str = new Str 'hello kitty'; # I dont believe this is possible although this is preferred.
$str = new Str; # get rid of the construct param.
$str = 'value here'; #instead of resetting, set 'value here' to Str::$value??
In the second method, is there a way i could possibly catch that variable bing set again and instead of reseting it, set this to Str::$value ? I have thought around and the closest i could come up to is the __destruct method. but there was no possible way to know how it was being destroyed. Is this possible or am i wasting my time?
Since PHP is loosely typed, there is no natural string class, because the natural way of using strings is, well, by just using them. However, as of PHP5.3 there is an extension in the SPL that provides strongly typed scalars:
http://php.net/manual/en/book.spl-types.php
However, keep in mind that this extension is marked experimental and subject to change. As of now, it is also not available on Windows.
You might also want to try https://github.com/nikic/scalar_objects
This extension implements the ability to register a class that handles the method calls to a certain primitive type (string, array, ...). As such it allows implementing APIs like $str->length().
Also See: https://github.com/alecgorge/PHP-String-Class
A good string class
It's impossible to call functions in PHP without parentheses.
Your next method will change the reference to string.
Why it doesn't look natural to you? It's the same way in Java.
You may find this useful:
php-string
I'm afraid to tell you that you won't have any luck with either of both.
$str = new Str 'hello kitty'; will end up in fatal error and though the second method is valid it doesn't do what you intend but rather reassign a native string.
May I ask why you would want to have a wrapper araound a native type?