PHP call_user_func versus just calling function

Question

I am sure there is a very simple explanation for this. What is the difference between the two:

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'); 

Answer 1

Always use the name of the actual function when you know it.

call_user_func intended for calling functions whose name you do not know in advance, but it is much less efficient, since the program must look for the function at run time.

Answer 2

Although you can call function variable names as follows:

 function printIt($str) { print($str); } $funcname = 'printIt'; $funcname('Hello world!'); 

There are times when you do not know how many arguments you pass. Consider the following:

 function someFunc() { $args = func_get_args(); // do something } call_user_func_array('someFunc',array('one','two','three')); 

It is also convenient for calling static and object methods, respectively:

 call_user_func(array('someClass','someFunc'),$arg); call_user_func(array($myObj,'someFunc'),$arg); 

Answer 3

there is a call_user_func option, so you can do things like:

 $dynamicFunctionName = "barber"; call_user_func($dynamicFunctionName, 'mushroom'); 

where the string dynamicFunctionName can be more exciting and generated at runtime. You should not use call_user_func if necessary because it is slower.

Answer 4

I suppose this is useful for calling a function that you do not know the name in advance ... Something like:

 switch($value): { case 7: $func = 'run'; break; default: $func = 'stop'; break; } call_user_func($func, 'stuff'); 

Answer 5

There are no advantages to calling such a function, because I think that it is mainly used to call the user function (for example, a plug-in), because editing the kernel file is not a good option. here is a dirty example used by wordpress

 <?php /* * my_plugin.php */ function myLocation($content){ return str_replace('@', 'world', $content); } function myName($content){ return $content."Tasikmalaya"; } add_filter('the_content', 'myLocation'); add_filter('the_content', 'myName'); ?> 

...

 <?php /* * core.php * read only */ $content = "hello @ my name is "; $listFunc = array(); // store user function to array (in my_plugin.php) function add_filter($fName, $funct) { $listFunc[$fName]= $funct; } // execute list user defined function function apply_filter($funct, $content) { global $listFunc; if(isset($listFunc)) { foreach($listFunc as $key => $value) { if($key == $funct) { $content = call_user_func($listFunc[$key], $content); } } } return $content; } function the_content() { $content = apply_filter('the_content', $content); echo $content; } ?> 

....

 <?php require_once("core.php"); require_once("my_plugin.php"); the_content(); // hello world my name is Tasikmalaya ?> 

Exit

 hello world my name is Tasikmalaya 

Answer 6

in the first example, you use the function name, which is a string. it can occur from the outside or be determined "on the fly." that is, you don’t know what function you will need to run at the time the code is created.

Answer 7

When using namespaces, call_user_func () is the only way to run a function that you don't know beforehand, for example:

 $function = '\Utilities\SearchTools::getCurrency'; call_user_func($function,'USA'); 

If all your functions were in the same namespace, this would not be such a problem, as you could use something like this:

 $function = 'getCurrency'; $function('USA'); 

Edit: Following @Jannis, stating that I was wrong, I did a bit more tests and didn't have 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 that the second method works for PHP 7, but not PHP 5.6.