Quadratic equation solver in php

[khalilou]

I am solving a SECOND DEGREE EQUATION in PHP, I used several conditions to be able to manage all the possibilities of results.
The issue that the equation is provided in string so the coefficients are interpreted by the rgex function as a string as a result when I convert the coefficients to integer the conversion will be equal to 0 and not 1.
Is it possible to manage this condition ?
I would like to find the best approach or regex function to solve this issue
here is my code :
https://onlinephp.io/c/52832
Thanks in advance