Introduction to the php input form that can only enter numbers

PHP is a popular scripting language often used for web development. In web development, forms are an important way of interaction. Forms provide a simple, flexible way for users to enter data and then pass that data to back-end programs for processing.

In PHP, the processing of form input data is very simple. However, sometimes we need to restrict user input data. For example, we may need to allow users to enter only numbers, not other characters such as letters, spaces, symbols, etc.

This article will introduce how to use PHP to control the form to only enter numbers.

1. Using HTML5 number input type

In HTML5, there is a special number type that can be used to limit the input content of the form. By setting the type attribute to number in the input box, you can require the user to enter only numbers.

<input type="number" name="age" min="0" max="150">

The above code will create a number input box named "age", requiring the input value to be between 0 and 150.

2. Use JavaScript to format user input

In some cases, we may want to restrict user input more strictly, such as only allowing integers to be entered Or only allow up to 2 decimal places to be entered. At this time, JavaScript can be used to format the user's input to ensure that the input data meets our requirements.

function check(event) {
    var code = event.keyCode;
    if ((code < 48 || code > 57) && code != 8 && code != 9 && code != 13 && code != 190 && code != 110) {
        event.preventDefault();
    }
}

The above code will create a JavaScript function called "check" that prevents the user from entering non-numeric characters and multiple decimal points. We can limit user input by binding this function to the onkeypress event of the input box.

<input type="text" name="amount" onkeypress="check(event)">

The above code will create a text input box named "amount" and bind the JavaScript function "check" to the onkeypress event of the input box to limit the user's input.

3. Validate user input in PHP

Although we can limit the content input by users in HTML and JavaScript, in order to ensure the integrity and correctness of the data Finally, we also need to validate user-entered data in PHP. We can use many built-in functions in PHP to verify input data, such as is_numeric(), ctype_digit(), etc.

$number = $_POST['number'];
if (!is_numeric($number)) {
    echo "Error! Please enter a valid number.";
}

The above code will get the parameter named "number" from the POST request. If the value of this parameter is not a number, an error message will be output.

To sum up, we can use HTML, JavaScript and PHP to restrict the data that users enter in the form. Through these methods, we can ensure that users can only enter numbers, ensuring the integrity and correctness of the data to the greatest extent.

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