$ foo = " 1 "； // $foo is a string type.

$ bar =(int)$ foo； // $bar is an integer

2. Built-in function mode

$ foo = " 1 "； // $foo is a string type.

$ bar = intval($ foo)； // $bar is an integer

3. Format string mode

$ foo = " 1 "； // $foo is a string type.

$bar = sprintf("%d "，$ foo)； // $bar is a string type