How is the “compact” function used in PHP?

The purpose of the compact() function is to create an array consisting of variable names and their values.

Here is how it is used:

compact(var1, var2, var3, ...)

The parameter can either be a string of the variable name or an array containing strings of variable names.

The compact() function checks the value of each parameter. If the variable name is found in the current symbol table, it will be added to the resulting array with the variable name as the key and the value as the value. If the variable name is not found in the current symbol table, a NOTICE level error will be issued.

Here is an example:

$name = "John";
$age = 25;

$result = compact("name", "age");
print_r($result);

// 输出：
// Array
// (
//    [name] => John
//    [age] => 25
// )

In the example above, the compact() function combines the values of variables $name and $age into an array, with the variable names as the keys and the variable values as the values. The final output is an associative array.

Please note that the compact() function only checks for variables in the current symbol table, so it can only be used to create an array of existing variables.