How to verify that regular expression only has numbers in php

php method to implement regular expression verification with only numbers: 1. Create a PHP sample file; 2. Create a string variable to be verified as "$num"; 3. Use the if statement to judge, "preg_match ()" function performs regular expression verification, the syntax is "if(preg_match('/\D/', $num))"; 4. Output the result through "echo".

Operating system for this tutorial: Windows 10 system, php8.1.3 version, Dell G3 computer.

php method to verify that regular expressions only have numbers:

1. Create a PHP sample file;

2. Create a string to be verified Variable;

3. Use the if statement to make judgments. The "preg_match()" function performs regular expression verification. The syntax is "if(preg_match('/\D/', $num))". According to the return Just verify the result.

The code is:

$num = "12345"; // 要验证的字符串
// 使用preg_match函数测试字符串是否包含除数字以外的字符
if (preg_match('/\D/', $num)) {
  echo "只能包含数字";
} else {
  echo "验证通过";
}

When run using the above example code, the output is "Verification passed" because we only passed numbers as input. And if the input contains any non-numeric characters such as letters, symbols, or spaces, the output will read "Can only contain numbers."

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