how to convert string to associative array?

i have this string datatype:

$mystring = "['def step1(self):\n\ttry:\n\t\tglobal testcaseResult\n\t\tassert self.Remedy.returnStatus\n\t\tassert self.Remedy.returnStatus\n\t\tprint(self.Remedy.returnMessage)\n\t self.MOSS IOS.element_wait_by_xpath_hide(self, mossDriver, action_msg, by_xpath, timeout=5)\n\t self.Remedy.ResolutionCatPopulation(self, driver, ResoCat1, ResoCat2, ResoCat3=None)\n@def step2(self):\n\tself.MOSS IOS.element_wait_by_xpath_get_text(self, mossDriver, action_msg, by_xpath, timeout=30)\n@def step3(self):\n\tself.MOSS IOS.element_wait_by_xpath_get_text(self, mossDriver, action_msg, by_xpath, timeout=30)\n']"

how do i make it store in an become associative array(My Goal):

$newAssociativeArray= array("def step1(self)"=>"\n\ttry:\n\t\tglobal testcaseResult\n\t\tassert self.Remedy.returnStatus\n\t\tassert self.Remedy.returnStatus\n\t\tprint(self.Remedy.returnMessage)\n\t self.MOSS IOS.element_wait_by_xpath_hide(self, mossDriver, action_msg, by_xpath, timeout=5)\n\t self.Remedy.ResolutionCatPopulation(self, driver, ResoCat1, ResoCat2, ResoCat3=None)\n", "def step2(self)"=>"\n\tself.MOSS IOS.element_wait_by_xpath_get_text(self, mossDriver, action_msg, by_xpath, timeout=30)\n", "def step3(self)"=>"\n\tself.MOSS IOS.element_wait_by_xpath_get_text(self, mossDriver, action_msg, by_xpath, timeout=30)\n");

what i did:

$explodearray = explode("@",$mystring);
$newAssociativeArray[$key] = array();
for($countnum = 0; $countnum<count($explodearray);$countnum++){

if (strpos($explodearray[$countnum],"def") !== FALSE) { 
    echo "Match found"; 
  $newAssociativeArray[$key]  = $explodearray[$countnum];
}
else{
    $newAssociativeArray[$key][] = $explodearray[$countnum];
}


}

print_r( $newAssociativeArray);