<?php
class testclass {
    function assign($var, $value) {
        $this->$var = $value;
    }
}

$testobj = new testclass();

$testobj->testvar = 20;
$testobj->assign("testvar", 30);
echo $testobj->testvar; // Result = 30 - very good!

$testobj->testarray["dim1"]["dim2"] = 20;
$testobj->assign("testarray[dim1][dim2]", 30);
echo $testobj->testarray["dim1"]["dim2"]; // Result = 20 - bad (should be 30)!
?>