php creating an input form and saving the data in databse and showing it

i am creating a website using php for stock managment when i added supplier form i have encoutered a error that when i enter info it deos not add the supplier and the page geos blank i need help to fix it i think it has to be related to querry or the database files or php models

i tried changing some code in data base and in add supplier php and nothing changed and also treid to delete some stuff

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source https://stackoverflow.com/questions/76984433/php-creating-an-input-form-and-saving-the-data-in-databse-and-showing-it