How to use PHP to implement a form that only inputs numbers

In web development, we often need user input data. For some forms, we only want users to enter numbers. How to achieve this? This article will introduce how to use PHP to implement a form that only inputs numbers.

1. Use regular expressions to verify input

Regular expressions are patterns composed of some characters and are used to match strings. By using regular expressions we can check if the user input conforms to the format we expect. In this case, we can use regular expressions to check if the user input is a numeric character.

In PHP, the regular expression matching function can be easily implemented using the preg_match() function. The following is an example:

// 提取用户输入数据
$user_input = $_POST["input"];

// 正则表达式，匹配纯数字
$pattern = "/^[0-9]+$/";

// 检查输入是否与正则表达式匹配
if(preg_match($pattern, $user_input)){
    echo "输入正确，是纯数字!";
}else{
    echo "输入错误，不是纯数字!";
}

The above code will extract the data named input submitted by the user's POST method, and then use regular expression matching to determine whether it is a pure number, and output the judgment result.

2. Use the filter_var() function to verify input

PHP also provides the filter_var() function, which can also be used to verify user input data. This function can check whether the input data conforms to the specified filter rules. Among them, FILTER_VALIDATE_INT is a filter for validating integers.

The following is a sample code that uses the filter_var() function to verify whether the input is an integer:

// 提取用户输入数据
$user_input = $_POST["input"];

// 定义过滤器
$filter = FILTER_VALIDATE_INT;

// 检查输入是否通过过滤器
if(filter_var($user_input, $filter) !== false){
    echo "输入正确，是整数!";
}else{
    echo "输入错误，不是整数!";
}

In the above code, we use the filter_var() function to verify whether the user input is an integer. If the input passes the verification of the FILTER_VALIDATE_INT filter, the output is "The input is correct, it is an integer!"; otherwise, the output is "The input is wrong, it is not an integer!".

3. Restrict the input of numbers to only numbers

In addition to using the verification method, we can also limit the user's input method to ensure that only numbers are entered. We can use the type attribute of the input element in HTML to limit user input.

The following is an example of an input element that only allows the input of numbers:

<input type="number" name="input" min="0" max="999">

In the above code, we use the type="number" attribute to restrict the user to only enter numbers. At the same time, through With min and max attributes, we can also limit the range of input numbers.

In summary, we have introduced three methods to implement a form that only inputs numbers, including using regular expressions to verify input, using the filter_var() function to verify input, and limiting input methods. Different methods are suitable for different scenarios, and developers can choose the appropriate method according to their own needs.

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