PHP If you implement a custom formula

Title, has been implemented in PHP with the user-defined ($a + $b *2-3* $c) calculation formula to the MySQL table, and then need to calculate, read the formula from the table, but now read out, can not use this formula, is treated as a string, how to handle, the variable is pre-set before the formula read out

Reply to discussion (solution)

Try using the eval () function

Try this with the eval () function, and there are other ways not to

Https://github.com/droptable/php-shunting-yard.git

Https://github.com/droptable/php-shunting-yard.git What is this? Can you be a little clearer.

The direct eval () function is available.

Https://github.com/droptable/php-shunting-yard.git What is this? Can you make it clear? You can see what he's saying, it's an expression parser.

You can use the Eval function in general.

If you're afraid of eval, you can write it in create_function parameters.

Look at this eval and think of a word of the Trojan horse

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