I have a code similar to this:
$name = '_DBR'; // This comes from a function call
$this->_Inits['_DBR'] = function () { return get_library('Database')->getConnection('users', 'read'); };
$inits = $this->_Inits[$name];
$result = $inits(); // ERROR: Function name must be a string
return $result;
The error I get is:
Function name must be a string in xxxx
Is there any ways I could use an array to store multiple closures and is there a working way to access them?
I use PHP 5.4.3
This works fine for me in php 5.3.10.
$m = array();
$m['fish'] = function() { print "Hello\n"; };
$f = $m['fish'];
$f();
Yeah, use call_user_func instead.
Related
I have this piece of code:
private function _resolveCustomEntries($fields)
{
foreach ($fields as &$value) {
if (array_key_exists('custom', $value)) {
if (method_exists($this, $value['custom'])) {
$value['custom'] = $this->$value['custom'](); //variableInterpolation
}
}
}
return $fields;
}
I ran a PHP 7.2 compatibility check and it complained here with the "variableInterpolation" on the marked line. When I run this code, the PHP log tells me this:
ERR (3): Notice: Array to string conversion in
/public_html/lib/KiTT/Payment/Widget.php on line 217
Thats the same line where the "variableInterpolation" check failed. So how would I rewrite this code so it works in PHP 7.2?
Thanks!
Solution:
$value['custom'] = $this->$value['custom']();
has to look like this:
$value['custom'] = $this->{$value['custom']}();
It's a matter of order variables are evaled.
With
class x {
public function y() {
echo 'ok';
}
}
$x = new x();
$y = array('i' => 'y');
Then
$x->$y['i']();
Fails because PHP first tries to cast the $y variable into a string, and get the matching property of $x (which btw does not exist), then tries to get the index 'i' or that unexisting property, and then tries to run it as a callable.
Hence 3 errors:
Array to string conversion
Undefined property x::$Array
Function name must be a string (nda: the undefined property returns NULL)
Instead, curly brace the variable to set the resolving order:
$x->$y['i']();
Will work. So use $this->{$value['custom']}()
This will throw an array to string conversion in 7.2
class bob{
function foo(){
return 'bar';
}
function getFoo(){
$value['custom'] = 'foo';
$value['custom'] = $this->$value['custom']();
return $value['custom'];
}
}
$bob = new Bob();
var_dump($bob->getFoo());
But it will execute just fine in 5.6.
Then i changed the snippet to this, not calling the method directly casting the array key to function name, but initializing a string (hopefully, there is no type validation in your code) variable with the function name first:
class bob{
function foo(){
return 'bar';
}
function getFoo(){
$value['custom'] = 'foo';
$functionName = $value['custom'];
$value['custom'] = $this->$functionName();
return $value['custom'];
}
}
$bob = new Bob();
var_dump($bob->getFoo());
This will run just fine in php 7.2
You could try rewriting your code using complex (curly) syntax, you can read more about it here.
Your code would look something like this.
$value['custom'] = $this->{$value['custom']}();
Edit: moved the curly braces to correct positions.
So I basically want to do this:
$this->container['Menu_builder'] = $this->container->factory(function ($c) {
return new Menu_builder($parameter_1, $parameter_2);
});
Where $parameter_1 and $parameter_2 are passed in from the call, like this:
$menu_builder = $this->container['Menu_builder']('account', 'reset_password');
I know the above syntax is incorrect, but I want to pass these strings into the call to $this->container->factory.
Is this possible?
For example, if I wanted to instantiate the Menu_builder from various controller functions with different parameters for each controller function.
FWIW, you can also include an anonymous function within your container.
$this->container['Menu_builder'] = function() {
// do stuff here
return function($parameter_1, $parameter_2) {
return new Menu_builder($parameter_1, $parameter_2);
};
};
Use this way:
$localfunc = $this->container['Menu_builder'];
$result = $localfunc($parameter_1, $parameter_2);
Notice that in this case I'm not using a factory. That's because you can execute the anonymous function with different values each time.
You just can use use() to pass your variables to the anonymous functions, e.g.
//your parameters needs to be defined here:
$parameter_1 = "XY";
$parameter_2 = 42;
$this->container['Menu_builder'] = $this->container->factory(function ($c)use($parameter_1, $parameter_2) {
//^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ See here
return new Menu_builder($parameter_1, $parameter_2);
});
Can non-anonymous functions in PHP using 'use' keyword? Or it is available for anonymous functions only.
Can I write a php file like this
// L.php
// assume $_texts is in this context..
$_language = null;
function L_init($language) use (&$_language)
{
$_language = $language;
}
function L($key) use ($_texts, $_language)
{
$_texts[$_language][$key];
}
So, another file can use it like this
// client.php
require_once 'L.php';
L_init('en');
echo L('GREETING'); // Will output localize string of key 'GREETING'
It is available for anonymous functions, but you can assign it to a variable:
$some_external_var = "World!";
$function = function() use($some_external_var){
echo "Hello ".$some_external_var;
};
Finally you can invoke it with:
call_user_func($function);
or just:
$function();
No you can't.
The code generate syntax errors.
Take a look at the following illustration:
// Trims input, fixes spaces and encodes bad glyphs. Also works with arrays.
function prepare_param($param)
{
$retval = "";
function prc($param)
{
$r = split(" ", trim($param));
foreach($r as $i => $e)
$r[$i] = urlencode($e);
return join("+", $r);
}
// If input is an array
if(is_array($param))
{
$retval = array();
foreach($param as $e)
$retval[] = prc($e);
}
// If input is a string
else if(is_string($param))
{
return prc($param);
}
else throw new Exception("Invalid input! Expected String or Array.");
}
Obviously the function prc will now be declared globally, even though declared inside a function. Is there a way to follow this principle, creating a tiny function/macro inside another function as not to litter the global scope? The alternative would be to make a class with a private function, which seems like overkill for my use.
Any help appreciated
You probably want closures, which are anonymous functions.
If you have PHP 5.3, enter anonymous functions:
$prc = function($param)
{
$r = split(" ", trim($param));
foreach($r as $i => $e)
$r[$i] = urlencode($e);
return join("+", $r);
};
if(is_array($param))
{
$retval = array();
foreach($param as $e)
$retval[] = $prc($e);
}
else if(is_string($param))
{
return $prc($param);
}
In this case, $prc only lives in the scope of your prepare_param() function.
If you have access to >=PHP 5.3, you can use anonymous functions, and if not, you can use create_function.
If you don't have PHP 5.3, you can use the create_function function.
There are two ways to do so. The closures/anonymous functions are possible from PHP 5.3, and the oldschool way would be to use create_function() - which is quite fugly.
However in your case, you don't want either. There is no benefit in creating or recreating the function. You just need it once, as it does not depend on any initialization state. The idiom you should use is called "dererred definition" and possible in PHP with:
if (!function_exists("prc")) {
function prc($param) {
...
}
}
You should name it with its parent function as prefix however (e.g. prepare__prc) to avoid clashes and to signalize its internal use.
Oh, and btw it could also be simplified compacted into:
$param = join("+", array_map("urlencode", split(" ", trim($param))));
anonymous functions might be what you are looking for
<?php
$greet = function($name)
{
printf("Hello %s\r\n", $name);
};
$greet('World');
$greet('PHP');
?>
If you don't use php 5.3 please be aware of the fact that the memory allocated by the "create_function()" function isn't released until the php process finishes. So if you create a lot of functions you might be running into issues.
In JavaScript, you can define anonymous functions that are executed immediately:
(function () { /* do something */ })()
Can you do something like that in PHP?
For versions prior to PHP 7, the only way to execute them immediately I can think of is
call_user_func(function() { echo 'executed'; });
With current versions of PHP, you can just do
(function() { echo 'executed'; })();
In PHP 7 is to do the same in javascript
$gen = (function() {
yield 1;
yield 2;
return 3;
})();
foreach ($gen as $val) {
echo $val, PHP_EOL;
}
echo $gen->getReturn(), PHP_EOL;
The output is:
1
2
3
This is the simplest for PHP 7.0 or later.
(function() {echo 'Hi';})();
It means create closure, then call it as function by following "()". Works just like JS thanks to uniform variable evaluation order.
https://3v4l.org/06EL3
Well of course you can use call_user_func, but there's still another pretty simple alternative:
<?php
// we simply need to write a simple function called run:
function run($f){
$f();
}
// and then we can use it like this:
run(function(){
echo "do something";
});
?>
(new ReflectionFunction(function() {
// body function
}))->invoke();
Note, accepted answer is fine but it takes 1.41x as long (41% slower) than declaring a function and calling it in two lines.
[I know it's not really a new answer but I felt it was valuable to add this somewhere for visitors.]
Details:
<?php
# Tags: benchmark, call_user_func, anonymous function
require_once("Benchmark.php");
bench(array(
'test1_anonfunc_call' => function(){
$f = function(){
$x = 123;
};
$f();
},
'test2_anonfunc_call_user_func' => function(){
call_user_func(
function(){
$x = 123;
}
);
}
), 10000);
?>
Results:
$ php test8.php
test1_anonfunc_call took 0.0081379413604736s (1228812.0001172/s)
test2_anonfunc_call_user_func took 0.011472940444946s (871616.13432805/s)
This isn't a direct answer, but a workaround. Using PHP >= 7. Defining an anonymous class with a named method and constructing the class and calling the method right away.
$var = (new class() { // Anonymous class
function cool() { // Named method
return 'neato';
}
})->cool(); // Instantiate the anonymous class and call the named method
echo $var; // Echos neato to console.
I tried it out this way, but it's more verbose than the top answer by using any operator (or function) that allows you to define the function first:
$value = $hack == ($hack = function(){
// just a hack way of executing an anonymous function
return array(0, 1, 2, 3);
}) ? $hack() : $hack();
Not executed inmediately, but close to ;)
<?php
$var = (function(){ echo 'do something'; });
$var();
?>