Check if number is positive | negative

is_num_negative.php

<?php
/*
 * Check number is positive
 * PHP Version required >= 4.0
 */
function is_num_negative( $num ){
    if( empty( trim( $num ) ) || ! is_numeric( $num ) ){
        return;
    }
    /*
     * Zero is number neutral
     * Example: If on a seesaw two people stay in middle, What happens? Do you understand?
     */
    if( $num <= -1 ){
        return true;
    }else{
        return;
    }
}

is_num_positive.php

<?php
/*
 * Check number is positive
 * PHP Version required >= 4.0
 */
function is_num_positive( $num ){
    if( empty( trim( $num ) ) || ! is_numeric( $num ) ){
        return;
    }
    /*
     * Zero is number neutral
     * Example: If on a seesaw two people stay in middle, What happens? Do you understand?
     */
    if( $num >= 1 ){
        return true;
    }else{
        return;
    }
}