validating-functions.php

<?php 

is_numeric( $var );       //http://php.net/manual/de/function.is-numeric.php
is_array( $var );         //http://php.net/manual/de/function.is-array.php
is_object( $var );        //http://php.net/manual/de/function.is-object.php
is_string( $var );        //http://php.net/manual/de/function.is-string.php


isset( $data['key'] );    //http://php.net/manual/de/function.isset.php
in_array( $var, $arr );   //http://php.net/manual/de/function.is-array.php
strlen( $var );           //http://php.net/manual/de/function.strlen.php
count( $arr);             //http://php.net/manual/de/function.count.php
empty( $var );            //http://php.net/manual/de/function.empty.php