PHP, How to catch a division by zero?

I have a large mathematical expression that has to be created dynamically. For example, once I have parsed "something" the result will be a string like: "$foo+$bar/$baz"; .

So, for calculating the result of that expression I'm using the eval function... something like this:

eval("$result = $expresion;");
echo "The result is: $result";

The problem here is that sometimes I get errors that says there was a division by zero, and I don't know how to catch that Exception. I have tried things like:

eval("try{$result = $expresion;}catch(Exception $e){$result = 0;}");
echo "The result is: $result";

Or:

try{
    eval("$result = $expresion;");
}
catch(Exception $e){
    $result = 0;
}
echo "The result is: $result";

But it does not work. So, how can I avoid that my application crashes when there is a division by zero?

Edit:

First, I want to clarify something: the expression is built dynamically, so I can't just eval if the denominator is zero. So... with regards to the Mark Baker's comment, let me give you an example. My parser could build something like this:

"$foo + $bar * ( $baz / ( $foz - $bak ) )"

The parser build the string step by step without worrying about the value of the vars... so in this case if $foz == $bak there's in fact a division by zero: $baz / ( 0 ) .

On the other hand as Pete suggested, I tried:

<?php
$a = 5;
$b = 0;

if(@eval(" try{ $res = $a/$b; } catch(Exception $e){}") === FALSE)
        $res = 0;
echo "$resn";
?> 

But it does not print anything.

---

if ($baz == 0.0) {
    echo 'Divisor is 0';
} else {
    ...
}

而不是使用eval，如果您在evalled表达式中使用用户输入，这是非常危险的，为什么不在PHPClasses上使用适当的解析器（如evalmath），并在除以零时引发干净的异常

---

Here's another solution:

<?php

function e($errno, $errstr, $errfile, $errline) {
    print "caught!n";
}

set_error_handler('e');

eval('echo 1/0;');

See set_error_handler()

---

您只需设置一个错误处理程序即可在发生错误时引发异常：

set_error_handler(function () {
    throw new Exception('Ach!');
});

try {
    $result = 4 / 0;
} catch( Exception $e ){
    echo "Divide by zero, I don't fear you!".PHP_EOL;
    $result = 0;
}

restore_error_handler();

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