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I've heard many places that PHP's eval function is often not the answer. In light of PHP 5.3's LSB and closures we're running out of reasons to depend on eval or create_function.
Are there any conceivable cases where eval is the best (only?) answer in PHP 5.3?
This question is not about whether eval is evil in general, as it obviously is not.
Summary of Answers:
var_export 
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Malicious code : invoking eval can crash a computer. For example: if you use eval server-side and a mischievous user decides to use an infinite loop as their username. Terribly slow : the JavaScript language is designed to use the full gamut of JavaScript types (numbers, functions, objects, etc)… Not just strings!
Eval function is mostly used in situations or applications which need to evaluate mathematical expressions. Also if the user wants to evaluate the string into code then can use eval function, because eval function evaluates the string expression and returns the integer as a result.
Definition and Usage The eval() method evaluates or executes an argument. If the argument is an expression, eval() evaluates the expression. If the argument is one or more JavaScript statements, eval() executes the statements.
An alternative to eval is Function() . Just like eval() , Function() takes some expression as a string for execution, except, rather than outputting the result directly, it returns an anonymous function to you that you can call. `Function() is a faster and more secure alternative to eval().
If you're writing malware and you want to make life hard for the sysadmin who's trying to clean up after you. That seems to be the most common usage case in my experience.
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Eric Lippert sums eval up over three blog posts. It's a very interesting read.
As far as I'm aware, the following are some of the only reasons eval is used.
For example, when you are building up complex mathematical expressions based on user input, or when you are serializing object state to a string so that it can be stored or transmitted, and reconstituted later.
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