The do-while loops are very similar to while loops, do-while loops checked the expression at the end of iteration.
do { //execute the statement; } while(expression)
$i = 1; do { echo $i++; } while ($i < 5); //output: 1234
The first iteration of a do-while loop is guaranteed to run because condition is checked at last
$i = 1; do { echo $i; } while ($i > 1); //output: 1