data_types.php

<?php
//Return `0` for `convert_to_int()`
//Return `0.0` for `convert_to_float()`
//Return an empty string for `convert_to_string()`
//Return `false` for `convert_to_bool()`
//Return `[]` for `convert_to_array()`
//Return `null` for `convert_to_null()`

$input = array('', array(''));

function convert_to_int($input){
 return (int)$input;
}


function convert_to_float($input){
  return (double)$input;
}

function convert_to_string($input){
 //array to string code here should return comma seperated values in a string
  if (is_array ($input)){
    $length = count($input);
    $output = "";

    for($i = 0; $i < $length; $i++){
      if($i+1 == $length) //checks if end of line removes last comma
      {$output .= $input[$i];}
      else{$output .= $input[$i] . ", ";}
    }
    return $output;
  }
  else{ return (string)$input;}
  // return (string)$input;
}

function convert_to_bool($input){
  return (bool)$input;
}

function convert_to_array($input){
  if ($input == null){
    return array();
  }
  //Test if Array return  -- else place in array
  elseif (is_array ($input)){
    return $input;}
  else{
    return array($input);}
}

function convert_to_null($input){
  if( $input == 0 || $input == false){
    return null;
  }else{return true;}
}

var_dump(convert_to_array($input));

?>