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Variable Variables with Functions - PHP

Quite possibly one of PHP’s least utilized yet most valuable features is its support for Variable Variables. In short these are a method of using the value of one variable to call the name of another. Sound confusing? We'll explain everything...

  1. Using Variable Variables in PHP
  2. Variable Variables?
  3. Using Variable Variables with Arrays
  4. Variable Variables with Functions
  5. Variable Variables with Classes
  6. The Never-ending Variable
  7. Conclusion
By: Eric Seufert
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February 14, 2001

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A great yet widely unused element of variable variables is their ability to be employed with functions. The function name can be set within a variable and then run through calling the variable variable of that variable. Here’s an example:

$function1 = "sort_stuff"; ${$function1()}; #this sets the result of the sort_stuff() function into a variable ${$function1($var1, $var2, $var3)}; #this does the same thing but sends the function parameters

Here’s a quick example of this in action, building on the same program segment I had introduced variable variables with:

$x = "Eric"; $$x = "Seufert"; $function = "value"; echo "${$function()}"; function value() { return "Eric"; }

This code would output:


as the echo statement is printing the value of the variable that gets created from the resultant of the value() function, "Eric". As we have already set $$x (which, following the variable variable, is the same as $Eric) to "Seufert", the same value is outputted, only this time resulting from a function call.

>>> More PHP Articles          >>> More By Eric Seufert

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