- strtotime: documentation ( source)
<?php
$run_time = '2016-10-27 10:00:00';
$entry_date = '2016-10-20 11:00:00';
$days_to_dial = 7*(1/24);
if ( ((strtotime($run_time)-strtotime($entry_date))/3600) >= $days_to_dial*24 ) {
echo strtotime($run_time).PHP_EOL;
echo strtotime($entry_date).PHP_EOL;
} else {
echo 'false';
}