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This article mainly introduces "how to quickly understand PHP filter". In daily operation, I believe many people have doubts about how to quickly understand PHP filter. The editor consulted all kinds of data and sorted out simple and easy-to-use operation methods. I hope it will be helpful for you to answer the doubts of "how to quickly understand PHP filter"! Next, please follow the editor to study!

PHP filter

What is a filter, you can simply understand the filter as filtering out unsafe data. Then why did we use it to be amazing? In our daily development, almost all Web applications rely on external input, usually from other applications like Web services or from users. We can ensure that the application can get the correct input type through the use of filters.

We should filter external data such as input data from the form, Cookies, server variables, and database query results. It is important to filter the input, so we need to use filters.

PHP filters are used to validate and filter data from non-secure sources, and are an important part of any Web application that tests, validates, and filters user input or custom data, and is designed to make data processing easier and faster.

Functions and filters

When we need to filter variables, we can use many filter functions: filter_var () filters a single variable through a specified filter; filter_var_array () filters multiple variables through the same or different filters; filter_input takes an input variable and filters it; filter_input_array takes multiple input variables and filters them through the same or different filters.

Next, let's take an example to see that an integer is validated by the filter_var () function, as follows:

Output result:

The above example validates an integer through the filter_var () filter function, and then take a look at the two commonly used filters.

Validating filter: used to validate user input, has strict formatting rules (such as URL or E-Mail validation), returns the expected type if successful, and returns FALSE if failed.

Sanitizing filter: used to allow or disable characters specified in a string, innumerable data format rules, always return a string.

Options and Flag

Options and flags are used to add additional filtering options to the specified filter. Different filters have different options and flags.

Next, let's take a look at validating an integer with the filter_var () and "min_range" and "max_range" options. The example is as follows:

Output result:

In the above example, it is important to note that, like the code above, the options must be placed in a related array called "options". If you use flags, you don't need to be in an array. Because the integer is "300", it is not within the specified range, so the output is as above.

Validate input

Next, let's try to validate the input from the form. The first thing we need to do is to confirm that there is the input data we are looking for. Then we use the filter_input () function to filter the input data.

Next, let's take an example to see that the input variable "email" is passed to the PHP page in the form of GET. The example is as follows:

Output result:

What we need to note is that the above example has an input variable (email) passed through the "GET" method to detect whether there is a "GET" type "email" input variable, and if there is an input variable, to detect whether it is a valid e-mail address.

Purifying input

Let's try to clean up the URL coming from the form. First, we need to make sure that there is the input data we are looking for. Then we use the filter_input () function to purify the input data.

Let's take an example to see that the input variable "url" is passed to the PHP page. The example is as follows:

Output result:

One of the things we need to pay attention to is:

The FILTER_SANITIZE_URL filter removes all illegal URL characters from the string. The above example has an input variable (url) passed through the "GET" method: detects the existence of a "url" input variable of type "GET", and if so, purifies it (removes illegal characters) and stores it in the $url variable.

At this point, the study on "how to quickly understand PHP filter" is over. I hope to be able to solve your doubts. The collocation of theory and practice can better help you learn, go and try it! If you want to continue to learn more related knowledge, please continue to follow the website, the editor will continue to work hard to bring you more practical articles!

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