Can you store a function in a PHP array?

The recommended way to do this is with an anonymous function:

$functions = [
  'function1' => function ($echo) {
        echo $echo;
   }
];

If you want to store a function that has already been declared then you can simply refer to it by name as a string:

function do_echo($echo) {
    echo $echo;
}

$functions = [
  'function1' => 'do_echo'
];

In ancient versions of PHP (<5.3) anonymous functions are not supported and you may need to resort to using create_function (deprecated since PHP 7.2):

$functions = array(
  'function1' => create_function('$echo', 'echo $echo;')
);

All of these methods are listed in the documentation under the callable pseudo-type.

Whichever you choose, the function can either be called directly (PHP ≥5.4) or with call_user_func/call_user_func_array:

$functions['function1']('Hello world!');

call_user_func($functions['function1'], 'Hello world!');

Since PHP "5.3.0 Anonymous functions become available", example of usage:

note that this is much faster than using old create_function...

//store anonymous function in an array variable e.g. $a["my_func"]
$a = array(
    "my_func" => function($param = "no parameter"){ 
        echo "In my function. Parameter: ".$param;
    }
);

//check if there is some function or method
if( is_callable( $a["my_func"] ) ) $a["my_func"](); 
    else echo "is not callable";
// OUTPUTS: "In my function. Parameter: no parameter"

echo "\n<br>"; //new line

if( is_callable( $a["my_func"] ) ) $a["my_func"]("Hi friend!"); 
    else echo "is not callable";
// OUTPUTS: "In my function. Parameter: Hi friend!"

echo "\n<br>"; //new line

if( is_callable( $a["somethingElse"] ) ) $a["somethingElse"]("Something else!"); 
    else echo "is not callable";
// OUTPUTS: "is not callable",(there is no function/method stored in $a["somethingElse"])

REFERENCES:

• Anonymous function: http://cz1.php.net/manual/en/functions.anonymous.php

• Test for callable: http://cz2.php.net/is_callable