Define constants
define('LOGENABLE', true);
Initialize an empty array
$arr = array();
Get the length of the array
$length = count($arr);
Output statement
echo, printf, print_r, var_dump
Introduce (call) other php
require(), include()
These two functions are basically the same, the difference is that require fails After that, a fatal error will be given, and after include fails, just a warning will be given.
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