I just simply want to create a function name with a string value.
Something like this:
$ns = 'test';
function $ns.'_this'(){}
test_this();
It of course throws an error.
I've tried with:
function {$ns}.'_this'
function {$ns.'_this'}
but no luck.
Any thoughts?
You can use create_function to create a function from provided string.
Example (php.net)
<?php
$newfunc = create_function('$a,$b', 'return "ln($a) + ln($b) = " . log($a * $b);');
echo "New anonymous function: $newfunc\n";
echo $newfunc(2, M_E) . "\n";
// outputs
// New anonymous function: lambda_1
// ln(2) + ln(2.718281828459) = 1.6931471805599
?>
This is not possible. If all you want to do is, to prefix all functions with some common string, maybe you want to use namespaces?
namespace foo {
function bar() {}
function rab() {}
function abr() {}
}
// access from global namespace is as follows:
namespace {
foo\bar(); foo\rab(); foo\abr();
}
file with function (somefile.php)
function outputFunctionCode($function_name)
{?>
function <?php echo $function_name ?>()
{
//your code
}
<?php }
file with code which "declares" the function:
ob_start();
include("somefile.php");
outputFunctionCode("myDynamicFunction");
$contents = ob_get_contents();
ob_end_clean();
$file = fopen("somefile2.php", "w");
fwrite($file,$contents);
fclose($file);
include("somefile2.php");
It is ugly, but then again, it is an extremely bad idea to declare functions with dynamic names.
using "eval" is not a good practice, but that may serve the purpose similar to your requirements sometimes.
<?php
$ns = 'test';
$funcName = $ns.'_this';
eval("function $funcName(){ echo 1;}");
test_this();
?>
Is this what you are looking for?
<?php
function foo($a) { print 'foo called'.$a; }
$myfunctionNameStr = 'foo';
$myfunctionNameStr(2);
?>
Cause i don't think that you can dynamically construct a function declaration. You can decide at 'runtime' the value of the $myfunctionNameStr though.
Related
I have a string variable
$worker_name = "video_convert"
I want to write a function with the name like the following
function video_convert(){
}
How can I do this in PHP? I tried
function eval($worker_name){
}
or
eval($worker_name) = function(){
}
But, it seems like it is not the correct way to do it in PHP.
You can do it as
$worker_name = 'video_convert';
$$worker_name = function() {
echo 'hi';
};
$$worker_name();
You could use call_user_func :
$worker_name ="video_convert"
function video_convert($text){
echo "Hello $text\n";
}
call_user_func($worker_name, 'World');
OR you could use the way you tried:
$worker_name = 'video_convert';
function video_convert(){
echo __METHOD__;
}
$worker_name();
OR like this:
$worker_name = function($text)
{
echo 'Anonymous function call '.$text
};
$worker_name('Hello');
PHP is flexible.
You can do somewhat like as
$worker_name = "video_convert";
function video_convert(){
echo "I've called a function using variable";
}
$worker_name();
If you want to use eval() function then use it by below way:-
$worker_name = "video_convert()";
function video_convert(){
echo "Called";
}
eval("$worker_name;");
How would I alter the function below to produce a new variable for use outside of the function?
PHP Function
function sizeShown ($size)
{
// *** Continental Adult Sizes ***
if (strpos($size, 'continental-')!== false)
{
$size = preg_replace("/\D+/", '', $size);
$searchsize = 'quantity_c_size_' . $size;
}
return $searchsize;
Example
<?php
sizeShown($size);
$searchsize;
?>
This currently produces a null value and Notice: undefined variable.
So the function takes one argument, a variable containing a string relating to size. It checks the variable for the string 'continental-', if found it trims the string of everything except the numbers. A new variable $searchsize is created which appends 'quantity_c_size_' to the value stored in $size.
So the result would be like so ... quantity_c_size_45
I want to be able to call $searchsize outside of the function within the same script.
Can anybody provide a solution?
Thanks.
Try using the global keyword, like so:
function test () {
global $test_var;
$test_var = 'Hello World!';
}
test();
echo $test_var;
However, this is usually not a good coding practice. So I would suggest the following:
function test () {
return 'Hello World!';
}
$test_var = test();
echo $test_var;
In the function 'sizeShown' you are just returning the function. You forgot to echo the function when you call your function.
echo sizeShown($size);
echo $searchsize;
?>
But the way you call $searchsize is not possible.
This is an old question, and I might not be understanding the OP's question properly, but why couldn't you just do this:
<?php
$searchsize = sizeShown($size);
?>
You're already returning $searchsize from the sizeShown method. So if you simply assign the result of the function to the $sizeShown variable, you should have what you want.
According to the most programming languages scope rules, I can access variables that are defined outside of functions inside them, but why doesn't this code work?
<?php
$data = 'My data';
function menugen() {
echo "[" . $data . "]";
}
menugen();
?>
The output is [].
To address the question as asked, it is not working because you need to declare which global variables you'll be accessing in the function itself:
$data = 'My data';
function menugen() {
global $data; // <-- Add this line
echo "[" . $data . "]";
}
menugen();
Otherwise you can access it as $GLOBALS['data'], see Variable scope.
Even if a little off-topic, I would suggest you avoid using globals at all and prefer passing data as parameters.
In this case, the above code look like this:
$data = 'My data';
function menugen($data) { // <-- Declare the parameter
echo "[" . $data . "]";
}
menugen($data); // <-- And pass it at call time
You can do one of the following:
<?php
$data = 'My data';
function menugen() {
global $data;
echo "[" . $data . "]";
}
menugen();
Or
<?php
$data = 'My data';
function menugen() {
echo "[" . $GLOBALS['data'] . "]";
}
menugen();
That being said, overuse of globals can lead to some poor code. It is usually better to pass in what you need. For example, instead of referencing a global database object you should pass in a handle to the database and act upon that. This is called dependency injection. It makes your life a lot easier when you implement automated testing (which you should).
Another way to do it:
<?php
$data = 'My data';
$menugen = function() use ($data) {
echo "[".$data."]";
};
$menugen();
UPDATE 2020-01-13: requested by Peter Mortensen
As of PHP 5.3.0 we have anonymous functions support that can create closures. A closure can access the variable which is created outside of its scope.
In the example, the closure is able to access $data because it was declared in the use clause.
It's a matter of scope. In short, global variables should be avoided so:
You either need to pass it as a parameter:
$data = 'My data';
function menugen($data)
{
echo $data;
}
Or have it in a class and access it
class MyClass
{
private $data = "";
function menugen()
{
echo this->data;
}
}
See #MatteoTassinari answer as well, as you can mark it as global to access it, but global variables are generally not required, so it would be wise to re-think your coding.
For many years I have always used this format:
<?php
$data = "Hello";
function sayHello(){
echo $GLOBALS["data"];
}
sayHello();
?>
I find it straightforward and easy to follow. The $GLOBALS is how PHP lets you reference a global variable. If you have used things like $_SERVER, $_POST, etc. then you have reference a global variable without knowing it.
I was looking for this answer, sort of, I wanted to see if anyone else had something similar with respect to how $prefix would be passed to an anonymous function. Seems the global scope is the the way? This is my solution for prefixing an array in a non-destructive manner.
private function array_prefix($prefix, $arr) {
$GLOBALS['prefix'] = $prefix;
return array_map(
function($ele) {
return $GLOBALS['prefix'].$ele;
},
$arr
);
}
<?php
$data = 'My data';
$menugen = function() use ($data) {
echo "[ $data ]";
};
$menugen();
?>
You can also simplify
echo "[" . $data . "]"
to
echo "[$data]"
PHP can be frustrating for this reason. The answers above using global did not work for me, and it took me awhile to figure out the proper use of use.
This is correct:
$functionName = function($stuff) use ($globalVar) {
//do stuff
}
$output = $functionName($stuff);
$otherOutput = $functionName($otherStuff);
This is incorrect:
function functionName($stuff) use ($globalVar) {
//do stuff
}
$output = functionName($stuff);
$otherOutput = functionName($otherStuff);
Using your specific example:
$data = 'My data';
$menugen = function() use ($data) {
echo "[" . $data . "]";
}
$menugen();
The proper way for accessing a global variable inside a function is answered above!
BUT if you do not want to use the global keyword, nor the $GLOBALS variable for some reason (for example you have multiple functions and you are "tired" of writing global $variable; every time), here is a workaround:
$variable = 42; // the global variable you want to access
// write a function which returns it
function getvar(){
global $variable;
return $variable;
}
//--------------
function func1()
{
// use that getter function to get the global variable
echo getvar(); // 42
}
function func2()
{
echo getvar(); // 42
}
...
You need to pass the variable into the function:
$data = 'My data';
function menugen($data)
{
echo $data;
}
I am trying to do something like this:
//function name
$str = 'bla()';
//make function with string as name
function $str{
echo 'yey';
}
//Call the function by string name
bla();
You could use eval() to attempt this task. But I really do NOT suggest it:
// name of the function
$str = 'bla';
// php code you want to execute inside
$inside = '';
eval("
function $str() { $inside }
");
Or you could also use an anonymous function:
$name = function() {
// code
};
// execution
$name();
Als if you are just trying to call a dynamic function just use call_user_func() like this:
// name of the function
$str = 'bla';
// paramters to the function
$param = array();
call_user_func($str, $param);
But I think you are doing something wrong. This kind of "hacks" are sign of bad application architecture.
References
eval()
call_user_func()
Anonymous functions
I'll suggest you, not to use like this. But if still you want to do this,
<?php
$greet = function($name)
{
printf("Hello %s\r\n", $name);
};
$greet('World');
$greet('PHP');
?>
Check here
And you are required to use PHP 5.3
Whenever a function completes, it RETURNS a value. If no value is set to be returned, 0 is returned.
If you would like to be able to do as you have asked, you could do the following:
function blah($string="Blah"){
return($string);
}
echo blah("Banana"); //echo's Banana
echo blah(); //echo's Blah
$str = blah("Apple"); //Sets $str to Apple
I'm sure there's a very easy explanation for this. What is the difference between this:
function barber($type){
echo "You wanted a $type haircut, no problem\n";
}
call_user_func('barber', "mushroom");
call_user_func('barber', "shave");
... and this (and what are the benefits?):
function barber($type){
echo "You wanted a $type haircut, no problem\n";
}
barber('mushroom');
barber('shave');
Always use the actual function name when you know it.
call_user_func is for calling functions whose name you don't know ahead of time but it is much less efficient since the program has to lookup the function at runtime.
Although you can call variable function names this way:
function printIt($str) { print($str); }
$funcname = 'printIt';
$funcname('Hello world!');
there are cases where you don't know how many arguments you're passing. Consider the following:
function someFunc() {
$args = func_get_args();
// do something
}
call_user_func_array('someFunc',array('one','two','three'));
It's also handy for calling static and object methods, respectively:
call_user_func(array('someClass','someFunc'),$arg);
call_user_func(array($myObj,'someFunc'),$arg);
the call_user_func option is there so you can do things like:
$dynamicFunctionName = "barber";
call_user_func($dynamicFunctionName, 'mushroom');
where the dynamicFunctionName string could be more exciting and generated at run-time. You shouldn't use call_user_func unless you have to, because it is slower.
With PHP 7 you can use the nicer variable-function syntax everywhere. It works with static/instance functions, and it can take an array of parameters. More info at https://trowski.com/2015/06/20/php-callable-paradox
$ret = $callable(...$params);
I imagine it is useful for calling a function that you don't know the name of in advance...
Something like:
switch($value):
{
case 7:
$func = 'run';
break;
default:
$func = 'stop';
break;
}
call_user_func($func, 'stuff');
There are no benefits to call it like that, the word user mean it is for multiple user, it is useful to create modification without editing in core engine.
it used by wordpress to call user function in plugins
<?php
/* main.php */
require("core.php");
require("my_plugin.php");
the_content(); // "Hello I live in Tasikmalaya"
...
<?php
/* core.php */
$listFunc = array();
$content = "Hello I live in ###";
function add_filter($fName, $funct)
{
global $listFunc;
$listFunc[$fName] = $funct;
}
function apply_filter($funct, $content)
{
global $listFunc;
foreach ($listFunc as $key => $value)
{
if ($key == $funct and is_callable($listFunc[$key]))
{
$content = call_user_func($listFunc[$key], $content);
}
}
echo $content;
}
function the_content()
{
global $content;
$content = apply_filter('the_content', $content);
echo $content;
}
....
<?php
/* my_plugin.php */
function changeMyLocation($content){
return str_replace('###', 'Tasikmalaya', $content);
}
add_filter('the_content', 'changeMyLocation');
in your first example you're using function name which is a string. it might come from outside or be determined on the fly. that is, you don't know what function will need to be run at the moment of the code creation.
When using namespaces, call_user_func() is the only way to run a function you don't know the name of beforehand, for example:
$function = '\Utilities\SearchTools::getCurrency';
call_user_func($function,'USA');
If all your functions were in the same namespace, then it wouldn't be such an issue, as you could use something like this:
$function = 'getCurrency';
$function('USA');
Edit:
Following #Jannis saying that I'm wrong I did a little more testing, and wasn't having much luck:
<?php
namespace Foo {
class Bar {
public static function getBar() {
return 'Bar';
}
}
echo "<h1>Bar: ".\Foo\Bar::getBar()."</h1>";
// outputs 'Bar: Bar'
$function = '\Foo\Bar::getBar';
echo "<h1>Bar: ".$function()."</h1>";
// outputs 'Fatal error: Call to undefined function \Foo\Bar::getBar()'
$function = '\Foo\Bar\getBar';
echo "<h1>Bar: ".$function()."</h1>";
// outputs 'Fatal error: Call to undefined function \foo\Bar\getBar()'
}
You can see the output results here: https://3v4l.org/iBERh it seems the second method works for PHP 7 onwards, but not PHP 5.6.