How to get a variable name as a string in PHP?

In this tutorial, we’re going to see how to get the name of a variable by accessing get_defined_vars().

There is no predefined function in PHP that can output the name of a variable. However, you can use the result of get_defined_vars(), which returns all the variables defined in the scope, including name and value.

Definition of your own function
    // Function for determining the name of a variable
    function getVarName(&$var, $definedVars=null) {
        $definedVars = (!is_array($definedVars) ? $GLOBALS : $definedVars);
        $val = $var;
        $rand = 1;
        while (in_array($rand, $definedVars, true)) {
            $rand = md5(mt_rand(10000, 1000000));
        $var = $rand;
        foreach ($definedVars as $dvName=>$dvVal) {
            if ($dvVal === $rand) {
                $var = $val;
                return $dvName;
        return null;
    // the name of $a is to be determined.   
    $a = 1;
    // Determine the name of $a
    echo getVarName($a);



The function getVarName() proceeds as follows:

  • The variable for which the name is to be determined is received as a reference. This is important because the value must be adjusted below.
  • The old value of the variable is saved.
  • The value of the variable is temporarily changed to a random value that does not yet appear among the defined variables.
  • The variable that has this random value is searched for among the defined variables.
  • The value of this variable is reset to the saved value.
  • The name of this variable is returned.
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getVarName() in the scope of a function

In the previous example, the function was called in the global scope (top level). In this case, the result of get_defined_vars() does not have to be transferred, the function then automatically uses $GLOBALS. However, if you are in a function, then get_defined_vars() must be used once.

    // insert the getVarName function from the previous example here
    function myfunction() 
        $a = 1;
        var_dump(getVarName($a)); // this call does not find $a
        var_dump(getVarName($a, get_defined_vars())); // with this it will be found


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