eval() evaluates the string
given in code_str as PHP
code. Among other things, this can be useful for storing code
in a database text field for later execution.
There are some factors to keep in mind when using eval(). Remember that the string passed
must be valid PHP code, including things like terminating
statements with a semicolon so the parser doesn't die on the
line after the eval(), and properly
escaping things in
code_str.
Also remember that variables given values under eval() will retain these values in the
main script afterwards.
A return statement will
terminate the evaluation of the string immediately. In PHP 4,
eval() returns
NULL unless return() is called in the evaluated
code, in which case the value passed to return()
is returned. In PHP 3, eval() does
not return a value.
提示: 任何直接把輸出到瀏覽器的結果,可使用輸出控制函數來擷取 此函數的輸出,在將之存入一個 字串(舉例說明)。