eval Evaluate a string as PHP code php函数


(PHP 4, PHP 5)

evalEvaluate a string as PHP code


mixed eval ( string $code_str )

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. To mix HTML output and PHP code you can use a closing PHP tag to leave PHP mode.

Also remember that variables given values under eval() will retain these values in the main script afterwards.



The code string to be evaluated. code_str does not have to contain PHP Opening tags.

A return statement will immediately terminate the evaluation of the string .


eval() returns NULL unless return is called in the evaluated code, in which case the value passed to return is returned. If there is a parse error in the evaluated code, eval() returns FALSE and execution of the following code continues normally. It is not possible to catch a parse error in eval() using set_error_handler().


Example #1 eval() example - simple text merge

$name 'coffee';
$str 'This is a $string with my $name in it.';
$str" ";
"$str = "$str";");
$str" ";


This is a $string with my $name in it.
This is a cup with my coffee in it.


Note: 因为是一个语言构造器而不是一个函数,不能被 可变函数 调用。


和直接将结果输出到浏览器一样,可使用输出控制函数来捕获当前函数的输出,然后(例如)保存到一个 string 中。


In case of a fatal error in the evaluated code, the whole script exits.


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