01_echo.php
02_print.php
03_vars.php
04_constants.php
05_comments.php
06_single_vs_double_quotes.php
07_integers.php
08_floats.php
09_boolens.php
10_strings.php
11_null.php
12_operators.php
13_states.php
14_loops.php
15_array.php
16_functions.php