How to call a function from a string stored in a variable

Question

I need to be able to call a function  but the function name is stored in a variable  is this possible  e g  function foo            code here    function bar            code here     functionName    quot foo quot      I need to call the function based on what is  functionName

User · Answer

In case someone else is brought here by google because they were trying to use a variable for a method within a class, the below is a code sample which will actually work. None of the above worked for my situation. The key difference is the & in the declaration of $c = & new... and &$c being passed in call_user_func.

My specific case is when implementing someone's code having to do with colors and two member methods lighten() and darken() from the csscolor.php class. For whatever reason, I wanted to have the same code be able to call lighten or darken rather than select it out with logic. This may be the result of my stubbornness to not just use if-else or to change the code calling this method.

$lightdark="lighten"; // or optionally can be darken
$color="fcc";   // a hex color
$percent=0.15;  
include_once("csscolor.php");
$c = & new CSS_Color($color);
$rtn=call_user_func( array(&$c,$lightdark),$color,$percent);

Note that trying anything with $c->{...} didn't work. Upon perusing the reader-contributed content at the bottom of php.net's page on call_user_func, I was able to piece together the above. Also, note that $params as an array didn't work for me:

// This doesn't work:
$params=Array($color,$percent);
$rtn=call_user_func( array(&$c,$lightdark),$params);

This above attempt would give a warning about the method expecting a 2nd argument (percent).

User · Answer

Yes  it is possible   function foo  msg        echo  msg   lt br   gt       var1    foo    var1  testing 1 2 3      Source  http   www onlamp com pub a php 2001 05 17 php foundations html page 2

User · Answer

What I learnt from this question and the answers  Thanks all   Let say I have these variables and functions    functionName1    sayHello    functionName2    sayHelloTo    functionName3    saySomethingTo     friend    John    datas   array       something   gt  how are you         to   gt  Sarah      function sayHello     echo  Hello       function sayHelloTo  to    echo  Dear  to  hello       function saySomethingTo  something   to    echo  Dear  to   something        To call function without arguments     Calling sayHello   call user func  functionName1         Hello   To call function with 1 argument     Calling sayHelloTo  John   call user func  functionName2   friend        Dear John  hello   To call function with 1 or more arguments This will be useful if you are dynamically calling your functions and each function have different number of arguments  This is my case that I have been looking for  and solved   call user func array is the key     You can add your arguments    1  statically by hard-code    arguments 0     how are you       my  something  arguments 1     Sarah      my  to     2  OR dynamically using foreach  arguments   NULL  foreach  datas as  data          arguments      data        Calling saySomethingTo  how are you     Sarah   call user func array  functionName3   arguments        Dear Sarah  how are you     Yay bye

User · Answer

A few years late  but this is the best manner now imho    x    new ReflectionFunction  foo   - gt getClosure     x

User · Answer

My favorite version is the inline version      variableName     12    className- gt   propertyName     className- gt   methodName       StaticClass     propertyName    StaticClass    methodName        You can place variables or expressions inside the brackets too

User · Answer

The easiest way to call a function safely using the name stored in a variable is     I want to call method deploy that is stored in functionname   functionname    deploy     retVal     functionname   parameters      I have used like below to create migration tables in Laravel dynamically   foreach App Test   columns as  name   gt   column            table- gt   column 0    name

User · Answer

functionName   or call user func  functionName

User · Answer

I dont know why u have to use that  doesnt sound so good to me at all  but if there are only a small amount of functions  you could use a if elseif construct  I dont know if a direct solution is possible   something like  foo    bar    test    foo   echo   test   should return bar  you can try around but i dont think this will work for functions

User · Answer

Use the call user func function

User · Answer

One unconventional approach  that came to my mind is  unless you are generating the whole code through some super ultra autonomous AI which writes itself  there are high chances that the functions which you want to  dynamically  call  are already defined in your code base  So why not just check for the string and do the infamous ifelse dance to summon the    you get my point   eg   if  functionName     foo      foo      else if  functionName     bar      bar        Even switch-case can be used if you don t like the bland taste of ifelse ladder   I understand that there are cases where the  dynamically calling the function  would be an absolute necessity  Like some recursive logic which modifies itself   But most of the everyday trivial use-cases can just be dodged    It weeds out a lot of uncertainty from your application  while giving you a chance to execute a fallback function if the string doesn t match any of the available functions  definition  IMHO

User · Answer

Dynamic function names and namespaces  Just to add a point about dynamic function names when using namespaces   If you re using namespaces  the following won t work except if your function is in the global namespace   namespace greetings   function hello            do something     myvar    hello    myvar       interpreted as   hello       What to do   You have to use call user func   instead      if hello   is in the current namespace call user func   NAMESPACE         myvar       if hello   is in another namespace call user func  mynamespace     myvar

User · Answer

Solution  Use PHP7 Note  For a summarized version  see TL DR at the end of the answer  Old Methods Update  One of the old methods explained here has been removed  Refer to other answers for explanation on other methods  it is not covered here  By the way  if this answer doesn t help you  you should return upgrading your stuff  PHP 5 6 support has ended in January 2019  now even PHP 7 1 and 7 2 are not being supported   See supported versions for more information  As others mentioned  in PHP5  and also in newer versions like PHP7  we could use variables as function names  use call user func   and call user func array    which  personally  I hate those functions   etc  New Methods As of PHP7  there are new ways introduced  Note  Everything inside  lt something gt  brackets means one or more expressions to form something  e g   lt function name gt  means expressions forming a function name  Dynamic Function Call  Function Name On-the-fly We can use one or more expressions inside parentheses as the function name in just one go  in the form of    lt function name gt   arguments    For example  function something    string       return  quot something quot       bar    quot some thing quot     str replace  quot   quot    quot  quot    bar         something     Possible  too  but generally  not recommended  because makes your code more complicated  str replace  quot   quot    quot  quot    bar          Note  Although removing the parentheses around str replace   is not an error  putting parentheses makes code more readable  However  you cannot do that sometimes  e g  while using   operator  To be consistent  I recommend you to put the parentheses always  Dynamic Method Call  Method Name On-the-fly Just like dynamic function calls  we can do the same way with method calls  surrounded by curly braces instead of parentheses  for extra forms  navigate to TL DR section    object- gt   lt method name gt   arguments    object    lt method name gt   arguments    See it in an example  class Foo       public function another    string               return  quot something quot             bar    quot another thing quot     new Something   - gt  explode  quot   quot    bar  0         something  Dynamic Method Call  The Array Syntax A more elegant way added in PHP7 is the following    lt object gt    lt method name gt   arguments     lt class name gt    lt method name gt   arguments      Static calls only  As an example  class Foo       public function nonStaticCall                 echo  quot Non-static call quot             public static function staticCall                 echo  quot Static call quot             x   new X       x   quot non quot     quot StaticCall quot         Non-static call   x   quot static quot     quot Call quot         Static call  Note  The benefit of using this method over the previous one is that  you don t care about the call type  i e  whether it s static or not   Note  If you care about performance  and micro-optimizations   don t use this method  As I tested  this method is really slower than other methods  more than 10 times   Extra Example  Using Anonymous Classes Making things a bit complicated  you could use a combination of anonymous classes and the features above   bar    quot SomeThing quot    echo  new class       public function something                 return 512          - gt  strtolower  bar         512  TL DR  Conclusion  Generally  in PHP7  using the following forms are all possible     Everything inside   lt something gt   brackets means one or more expressions    to form something     Dynamic function call   lt function name gt   arguments      Dynamic method call on an object  object- gt   lt method name gt   arguments   object    lt method name gt   arguments      Dynamic method call on a dynamically-generated object   lt object gt  - gt   lt method name gt   arguments    lt object gt      lt method name gt   arguments      Dynamic method call  statically ClassName    lt method name gt   arguments    lt class name gt      lt method name gt   arguments      Dynamic method call  array-like  no different between static and non-static calls   lt object gt    lt method name gt   arguments      Dynamic method call  array-like  statically   lt class name gt    lt method name gt   arguments   Special thanks to this PHP talk

User · Answer

For the sake of completeness  you can also use eval      functionName    foo     eval  functionName     However  call user func   is the proper way

User · Answer

Following code can help to write dynamic function in PHP  now the function name can be dynamically change by variable   current page     current page    home page    function       current page     page versions     function   function         echo  current page       function

User · Answer

Complementing the answer of  Chris K if you want to call an object s method  you can call it using a single variable with the help of a closure   function get method  object   method       return function   use  object   method            args   func get args            return call user func array array  object   method    args                        class test               function echo this  text           echo  text            test   new test     echo   get method  test   echo this     echo  Hello       Output is  Hello    I posted another example here

User · Answer

As already mentioned  there are a few ways to achieve this with possibly the safest method being call user func   or if you must you can also go down the route of  function name    It is possible to pass arguments using both of these methods as so   function name    foobar     function name arg1  arg2    call user func array  function name  array arg1  arg2      If the function you are calling belongs to an object you can still use either of these   object- gt  function name arg1  arg2    call user func array array  object   function name   array arg1  arg2      However if you are going to use the  function name   method it may be a good idea to test for the existence of the function if the name is in any way dynamic  if method exists  object   function name          object- gt  function name arg1  arg2

[php] How to call a function from a string stored in a variable?

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