I have a function which takes in about 10 arguments, in which most of them are optional. I was wondering if I could implement it in such a way that the user of the function does not need to bother with the order of the parameters.
For example:
public function foo($arg1, $arg2, $arg3='',$arg4='', $arg5='', $arg6='', $arg7=''){}
Now, when I use this function I can simply
$this->foo($arg1val, $arg2val, $arg6val);
Is there a way in php to do so?
Here is how I implemented this:
I've listed the parameters accepted by the function in the API, so the user can pass the parameters in any order in an array with key=>value pairs.
For example:
public function argumentsFilter($origParams, $newParams){
$tmpArr = array();
foreach ($origParams as $origKey){
foreach($newParams as $newKey => $newVal){
if($newKey == $origKey){
$tmpArr[$origKey] = $newVal;
}
}
if(empty($tmpArr[$origKey])){
$tmpArr[$origKey] = '';
}
}
return $tmpArr;
}
public function foo($arg1, $arg2, $arg=array()){
$validArgList = array('arg3', 'arg4', 'arg5', 'arg6', 'arg7');
$correctedArgList = $this->argumentsFilter($validArgList, $arg);
}
Is there a more elegant way to do this?
10 parameters for a function is clearly too much. Pass arrays instead:
function foo(array $params) {
$defaults = array('foo' => true, 'bar' => false, ...);
$params = array_intersect_key($params, $defaults) + $defaults;
// work with $params['foo']
// maybe extract($params)
}
This example shows a function that accepts an arbitrary number of "named parameter" in any order, filters invalid values and establishes defaults values.
It is not possible, since php doesn't support named arguments.
You have 2 choices: to use array or to redesign your function so it has fewer parameters (the latter is preferred).
There are many ways to do that, but I recommend this method:
function doSomething($required, /*optional*/ $arguments = array()) {
$arguments = array_merge(array(
// set defaults
"argument" => "default value",
), $arguments);
var_dump($arguments);
}
It is very clean and easy to understand.
Related
Is there a way in PHP to use a function which has optional parameters in its declaration where I do not have to pass an optional arguments which already have values declared and just pass the next argument(s) which have different values that are further down the parameter list.
Assuming I have a function that has 4 arguments, 2 mandatory, 2 optional. I don't want to use null values for the optional arguments. In usage, there are cases where I want to use the function and the value of the 3rd argument is the same as the default value but the value of the 4th argument is different.
I am looking for a not so verbose solution that allows me to just pass the argument that differs from the default value without considering the order in the function declaration.
createUrl($host, $path, $protocol='http', $port = 80) {
//doSomething
return $protocol.'://'.$host.':'.$port.'/'.$path;
}
I find myself repeating declaring variables so that I could use a function i.e to use $port, I redeclare $protocol with the default value outside the function scope i.e
$protocol = "http";
$port = 8080;
Is there any way to pass the 2nd optional parameter($port) without passing $protocol and it would "automatically" fill in the default value of $protocol i.e
getHttpUrl($server, $path, $port);
This is possible in some languages like Dart in the form of Named Optional parameters.See usage in this SO thread. Is their a similar solution in PHP
You could potentially use a variadic function for this.
Example:
<?php
function myFunc(...$args){
$sum = 0;
foreach ($args as $arg) {
$sum += $arg;
}
return $sum;
}
Documentation:
http://php.net/manual/en/functions.arguments.php#functions.variable-arg-list
PHP doesn't allow at this state to call functions parameters in the order we want.Maybe in the future it will.However you can easily achieve your purpose by using an associative array as the only argument, and then define, the default parameter in the function.For the call you will need to pass an array with only the values which interest you.This array will be merged with the default array.You can even implement required parameters and call them in any order you want.
example:
function mysweetcode($argument){
$required=['first'];//specify required parameters here
$default=['first'=>0,'second'=>1,'third'=>2];//define all parameters with their default values here
$missing=[];
if(!is_array($argument)) return false;
$argument=array_intersect_key($argument,$default);
foreach($required as $k=>$v){//check for missing required parameters
if(!isset($argument[$v]))
$missing[]=$v;
}
if(!empty($missing)){// if required are missing trigger or throw error according to the PHP version
$cm=count($missing);
if (version_compare(PHP_VERSION, '7.0.0') < 0) {
trigger_error(call_user_func_array('sprintf',
array_merge(array('Required '.(($cm>1)?'parameters:':'parameter:').
str_repeat('%s,',$cm).(($cm>1)?' are':' is').' missing'),$missing)),
E_USER_ERROR);
}else{
throw new Error(call_user_func_array('sprintf',array_merge(
array('Required '.(($cm>1)?'parameters:':'parameter:').
str_repeat('%s',$cm).(($cm>1)?' are':' is').' missing'),$missing)));
}
}
$default=array_merge($default,$argument);//assign given values to parameters
extract($default);/*extract the parameters to allow further checking
and other operations in the function or method*/
unset($required,$missing,$argument,$default,$k,$v);//gain some space
//then you can use $first,$second,$third in your code
return $first+$second+$third;
}
var_dump(mysweetcode(['first'=>9,'third'=>8]));//the output is 18
var_dump(mysweetcode(['third'=>8]));//this throws Error on PHP7 and trigger fatal error on PHP5
You can check a live working code here
Well, this should work:
function myFunc($arg1, $arg2, $arg3=null, $arg4= null){
if ( is_null( $arg3 ) && is_null( $arg4 ) {
$arg3 = 3;
$arg4 = 4;
} else if ( is_null( $arg4 ) ) {
$arg4 = $arg3;
$arg3 = 3;
}
echo $arg1 + $arg2 + $arg3 + $arg4;
}
However I suggest you to rethink your problem (as a whole) because this is not a very good idea.
You could refactor this to use a parameter object; this way, you could include the default parameters in this object and set them in any order (with a trade-off of more verbose code). As an example using your above code,
<?php
class AdditionParameters
{
private $arg1 = 0;
private $arg2 = 0;
private $arg3 = 3;
private $arg4 = 4;
public function getArg1() { return $this->arg1; }
public function getArg2() { return $this->arg2; }
public function getArg3() { return $this->arg3; }
public function getArg4() { return $this->arg4; }
public function setArg1($value) { $this->arg1 = $value; return $this; }
public function setArg2($value) { $this->arg2 = $value; return $this; }
public function setArg3($value) { $this->arg3 = $value; return $this; }
public function setArg4($value) { $this->arg4 = $value; return $this; }
}
From there, you could simply call the function while passing in this new object.
function myFunc(AdditionParameters $request) {
return $request->getArg1()
+ $request->getArg2()
+ $request->getArg3()
+ $request->getArg4();
}
echo myFunc((new AdditionParameters)->setArg1(1)->setArg2(2)->setArg4(6));
// or echo myFunc((new AdditionParameters)->setArg1(1)->setArg4(6)->setArg2(2));
Otherwise, PHP doesn't allow you to have named optional parameters. (e.g. myFunc(1, 2, DEFAULT, 4);)
You have the response in your question, you can declare your function like
function myFunc($arg1, $arg2, $arg3 = null, $arg4 = null){
//here you check if the $arg3 and $arg4 are null
}
then you call your function using
myFunc($arg1, $arg2);
There is no such way in PHP(like in python for example).
You have to use some tricks in order to do that but will not always work.
For example:
// creates instances of a class with $properties.
// if $times is bigger than 1 an array of instances will be returned instead.(this is just an example function)
function getInstance($class, $properties = [], $times = 1){
//my code
}
$user = getInstance("User", ["name" => "John"]); // get one instance
$users = getInstance("User", ["name" => "John"],2); // get two instances.
If you want to use the function without passing the $parameters argument, like this:
$users = getInstance("User",2);
you can change the function to:
// creates instances of a class with $properties.
// if times is bigger than 1 an array of instances will be returned instead.
function getInstance($class, $properties = [], $times = 1){
if(is_numberic($properties)){
$times = $properties;
$properties = [];
}
//my code
}
Of course, this strategy will work only if you parameters have different types.
PS. This method is use in the Laravel Framework a lot. From there I got the inspiration.
This is modified from one of the answers and allows arguments to be added in any order using associative arrays for the optional arguments
function createUrl($host, $path, $argument = []){
$optionalArgs = [
'protocol'=>'http',
'port'=>80];
if( !is_array ($argument) ) return false;
$argument = array_intersect_key($argument,$optionalArgs);
$optionalArgs = array_merge($optionalArgs,$argument);
extract($optionalArgs);
return $protocol.'://'.$host.':'.$port.'/'.$path;
}
//No arguments with function call
echo createUrl ("www.example.com",'no-arguments');
// returns http://www.example.com:80/no-arguments
$argList=['port'=>9000];
//using port argument only
echo createUrl ("www.example.com",'one-args', $argList);
//returns http://www.example.com:9000/one-args
//Use of both parameters as arguments. Order does not matter
$argList2 = ['port'=>8080,'protocol'=>'ftp'];
echo createUrl ("www.example.com",'two-args-no-order', $argList2);
//returns ftp://www.example.com:8080/two-args-no-order
As of version 8.0, PHP now has named arguments. If you name the arguments when calling the function, you can pass them in any order and you can skip earlier default values without having to explicitly pass a value for them.
For example:
function createUrl($host, $path, $protocol = 'http', $port = 80)
{
return "$protocol://$host:$port/$path";
}
createUrl(host: 'example.com', path: 'foo/bar', port: 8080);
// returns: "http://example.com:8080/foo/bar"
From very long time i am working on php.
But one question may I have no idea about
like I have one function as bellow:
function hello($param1, $param2="2", $param3="3", $param4="4")
Now whenever I will use this function and if I need 4th params thats the $param4 then still I need to call all as blank like this one:
hello(1, '', '', "param4");
So is there any another way to just pass 1st and 4th param in call rather then long list of blanks ?
Or is there any other standard way for this ?
There was an RFC for this named skipparams but it was declined.
PHP has no syntactic sugar such as hello(1, , , "param4"); nor hello(1, default, default, "param4"); (per the RFC) for skipping optional parameters when calling a function.
If this is your own function then you can choose the common jQuery style of passing options into plug-ins like this:
function hello( $param1, $more_params = [] )
{
static $default_params = [
'param2' => '2',
'param3' => '3',
'param4' => '4'
];
$more_params = array_merge( $default_params, $more_params );
}
Now you can:
hello( 1, [ 'param4'=>'not 4, muahaha!' ] );
If your function requires some advanced stuff such as type hinting then instead of array_merge() you will need to manually loop $more_params and enforce the types.
One potential way you can do this, while a little bit hacky, may work well in some situations.
Instead of passing multiple variables, pass a single array variable, and inside the function check if the specific keys exist.
function hello($param1, $variables = ["param2" => "2", "param3" => "3", "param4" => "4"]) {
if(!array_key_exists("param2", $variables)) $variables['param2'] = "2";
if(!array_key_exists("param3", $variables)) $variables['param3'] = "3";
if(!array_key_exists("param4", $variables)) $variables['param4'] = "4";
echo "<pre>".print_r($variables, true)."</pre>";
}
This will allow you to set "param4" in the above variable, while still remaining default on all of the others.
Calling the function this way:
hello("test", ["param4" => "filling in variable 4"]);
Will result in the output being:
Array
(
[param4] => filling in variable 4
[param2] => 2
[param3] => 3
)
I don't generally recommend this if it can be avoided, but if you absolutely need this functionality, this may work for you.
The key here is that you have a specifically named index inside the array being passed, that you can check against inside the function itself.
The answer, as I see it, is yes and no.
No, because there's no way to do this in a standard fashion.
Yes, because you can hack around it. This is hacky, but it works ;)
Example:
function some_call($parm1, $parm2='', $parm3='', $parm4='') { ... }
and the sauce:
function some_call_4($parm1, $parm4) {
return some_call($parm1, '', '', $parm4);
}
So if you make that call ALOT and are tired of typing it out, you can just hack around it.
Sorry, that's all I've got for you.
It is an overhead, but you can use ReflectionFunction to create a class, instance of which that can be invoked with named parameters:
final class FunctionWithNamedParams
{
private $func;
public function __construct($func)
{
$this->func = $func;
}
public function __invoke($params = [])
{
return ($this->func)(...$this->resolveParams($params));
}
private function resolveParams($params)
{
$rf = new ReflectionFunction($this->func);
return array_reduce(
$rf->getParameters(),
function ($carry, $param) use ($params) {
if (isset($params[$param->getName()])) {
$carry[] = $params[$param->getName()];
} else if ($param->isDefaultValueAvailable()) {
$carry[] = $param->getDefaultValue();
} else {
throw new BadFunctionCallException;
}
return $carry;
},
[]
);
}
}
Then you can use it like this:
function hello($param1, $param2 = "2", $param3 = "3", $param4 = "4")
{
var_dump($param1, $param2, $param3, $param4);
}
$func = new FunctionWithNamedParams('hello');
$func(['param1' => '1', 'param4' => 'foo']);
Here is the demo.
I have an associative array in the following form:
$params = array(
'paramName_4'=>'param_4',
'paramName_2'=>'param_2',
// ...,
'paramName_6'=>'param_6',
);
and I also have a function myFunction defined as:
public function myFunction($paramName_1, $paramName_2, $paramName_3, ....);
Does a a "parsing" function exist in PHP so that I can call function myFunction by matching the parameters (even if they are not sorted wrt the myFunction's parameter sequence)? In other words, can I do
my_magic(__NAMESPACE__.'\\myFunction', $params);
Does this "magic" function does exist? If not, how can I implement it?
You can implement it using reflection. Here's how:
// The input is the array of arguments and the function name
$arguments = array(....);
$functionName = __NAMESPACE__.'\\myFunction';
$reflector = new \ReflectionFunction($functioName);
$params = $reflector->getParameters();
$values = array();
foreach ($params as $param) {
$name = $param->getName();
$isArgumentGiven = array_key_exists($name, $arguments);
if (!$isArgumentGiven && !$param->isDefaultValueAvailable() {
die ("Parameter $name is mandatory but was not provided");
}
$values[$param->getPosition()] =
$isArgumentGiven ? $arguments[$name] : $param->getDefaultValue();
}
// You can now call the function:
call_user_func($functionName, $values);
Yes, you can use Reflection as per #Jon's example, but if the problem is just that the params aren't in the right order, why not just use ksort() or uksort() to put them in the right order.
Then you can use call_user_func_array(). Problem solved.
$params = array(....);
uksort($params, function($a,$b) {
//sort the params into the known order....
$sortOrder = array('param1','param2','param3','param4');
return (array_search($a, $sortOrder) > array_search($b, $sortOrder)) ? -1 : 1;
});
//now that $params is in the right order we can do this....
$retVal = call_user_func_array($func, $params);
I've hard-coded the param order here, because it's the most efficient way. If you are calling a function where you don't know the correct param order in advance, then yes, you'll need to use reflection. But I would think that's fairly unlikely (passing an unknown params list into an unknown function sounds like a goldmine for hackers)
Here is a library which does the argument resolving for a given function/method: ArgumentsResolver.
I can't seem to find anything of this, and was wondering if it's possible to store a function or function reference as a value for an array element. For e.g.
array("someFunc" => &x(), "anotherFunc" => $this->anotherFunc())
Thanks!
You can "reference" any function. A function reference is not a reference in the sense of "address in memory" or something. It's merely the name of the function.
<?php
$functions = array(
'regular' => 'strlen',
'class_function' => array('ClassName', 'functionName'),
'object_method' => array($object, 'methodName'),
'closure' => function($foo) {
return $foo;
},
);
// while this works
$functions['regular']();
// this doesn't
$functions['class_function']();
// to make this work across the board, you'll need either
call_user_func($functions['object_method'], $arg1, $arg2, $arg3);
// or
call_user_func_array($functions['object_method'], array($arg1, $arg2, $arg3));
PHP supports the concept of variable functions, so you can do something like this:
function foo() { echo "bar"; }
$array = array('fun' => 'foo');
$array['fun']();
Yout can check more examples in manual.
Yes, you can:
$array = array(
'func' => function($var) { return $var * 2; },
);
var_dump($array['func'](2));
This does, of course, require PHP anonymous function support, which arrived with PHP version 5.3.0. This is going to leave you with quite unreadable code though.
check out PHP's call_user_func. consider the below example.
consider two functions
function a($param)
{
return $param;
}
function b($param)
{
return $param;
}
$array = array('a' => 'first function param', 'b' => 'second function param');
now if you want to execute all the function in a sequence you can do it with a loop.
foreach($array as $functionName => $param) {
call_user_func($functioName, $param);
}
plus array can hold any data type, be it function call, nested arrays, object, string, integer etc. etc.
I know that it is possible to call a function with a variable number of parameters with call_user_func_array() found here -> http://php.net/manual/en/function.call-user-func-array.php . What I want to do is nearly identical, but instead of a function, I want to call a PHP class with a variable number of parameters in it's constructor.
It would work something like the below, but I won't know the number of parameters, so I won't know how to instantiate the class.
<?php
//The class name will be pulled dynamically from another source
$myClass = '\Some\Dynamically\Generated\Class';
//The parameters will also be pulled from another source, for simplicity I
//have used two parameters. There could be 0, 1, 2, N, ... parameters
$myParameters = array ('dynamicparam1', 'dynamicparam2');
//The instantiated class needs to be called with 0, 1, 2, N, ... parameters
//not just two parameters.
$myClassInstance = new $myClass($myParameters[0], $myParameters[1]);
You can do the following using ReflectionClass
$myClass = '\Some\Dynamically\Generated\a';
$myParameters = array ('dynamicparam1', 'dynamicparam2');
$reflection = new \ReflectionClass($myClass);
$myClassInstance = $reflection->newInstanceArgs($myParameters);
PHP manual: http://www.php.net/manual/en/reflectionclass.newinstanceargs.php
Edit:
In php 5.6 you can achieve this with Argument unpacking.
$myClass = '\Some\Dynamically\Generated\a';
$myParameters = ['dynamicparam1', 'dynamicparam2'];
$myClassInstance = new $myClass(...$myParameters);
I implement this approach a lot when function args are > 2, rather then end up with an Christmas list of arguments which must be in a specific order, I simply pass in an associative array. By passing in an associative array, I can check for necessary and optional args and handle missing values as needed. Something like:
class MyClass
{
protected $requiredArg1;
protected $optionalArg1;
public function __construct(array $options = array())
{
// Check for a necessary arg
if (!isset($options['requiredArg1'])) {
throw new Exception('Missing requiredArg1');
}
// Now I can just localize
$requiredArg1 = $options['requiredArg1'];
$optionalArg1 = (isset($options['optionalArg1'])) ? $options['optionalArg1'] : null;
// Now that you have localized args, do what you want
$this->requiredArg1 = $requiredArg1;
$this->optionalArg1 = $optionalArg1;
}
}
// Example call
$class = 'MyClass';
$array = array('requiredArg1' => 'Foo!', 'optionalArg1' => 'Bar!');
$instance = new $class($array);
var_dump($instance->getRequiredArg1());
var_dump($instance->getOptionalArg1());
I highly recommend using an associative array, however it is possible to use a 0-index array. You will have to be extremely careful when constructing the array and account for indices that have meaning, otherwise you will pass in an array with offset args and wreck havoc with your function.
You can do that using func_get_args().
class my_class {
function __construct( $first = NULL ) {
$params = func_get_args();
if( is_array( $first ) )
$params = $first;
// the $params array will contain the
// arguments passed to the child function
foreach( $params as $p )
echo "Param: $p\n";
}
}
function my_function() {
$instance = new my_class( func_get_args() );
}
echo "you can still create my_class instances like normal:";
$instance = new my_class( "one", "two", "three" );
echo "\n\n\n";
echo "but also through my_function:";
my_function( "one", "two", "three" );
Basically, you simply pass the result of func_get_args to the constructor of your class, and let it decide whether it is being called with an array of arguments from that function, or whether it is being called normally.
This code outputs
you can still create my_class instances like normal:
Param: one
Param: two
Param: three
but also through my_function:
Param: one
Param: two
Param: three
Hope that helps.
I've found here
Is there a call_user_func() equivalent to create a new class instance?
the example:
function createInstance($className, array $arguments = array())
{
if(class_exists($className)) {
return call_user_func_array(array(
new ReflectionClass($className), 'newInstance'),
$arguments);
}
return false;
}
But can somebody tell me if there is an example for classes with protected constructors?