How to make a calculator in PHP?
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by
Giulio Muscarello
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Published on 2012-10-02T14:52:39Z
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2012/10/02
15:37 UTC
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php
I want to use PHP to calculate simple algebraic expressions like, 8*(5+1)
, entered via an <input>
tag by a normal user (which means, normal notation: no syntax changes like Multiply(8, Add(5, 1)))
. Also, it has to show all steps, but that's not hard. The problem, right now, is calculating the value of the expressions.
Note: this is what I thought so far, which is quite inefficient but it's a provisory solution.
Just replace strings where possible: in our example, recognize the string 5+1
and replace it with 6
. Then, loop again, replace (6)
with 6
, loop again, and replace 8*6
with 48
.
The code for multiplying, for example, should look like this:
for ($a=1; $a < 1000; $a++) {
for ($b=1; $b < 1000; $b++) {
string_replace($a . '*' . $b, $a*$b, $string);
}
}
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