How to verify if a URL contains a specified string using regular expressions in PHP

With the development of the Internet, URLs have become an indispensable part of people's daily lives. Sometimes, we need to validate a URL to determine if it contains a specific string. In PHP, you can use regular expressions to perform this process. This article will introduce how to use regular expressions to verify whether a URL contains a specified string in PHP.

First, we need to understand some basic concepts in regular expressions. Regular expressions are expressions used to match string patterns. It is a special syntax that uses some special characters in the pattern to match strings. In PHP, we use the preg_match function for regular expression matching.

Here is a simple example showing how to check if the URL starts with http or https:

$url = "https://www.example.com";
if(preg_match("/^http(s)?:///i", $url)) {
    echo "URL is valid!";
} else {
    echo "URL is not valid!";
}

In the above code, we used the regular expression "/^http(s) ?:///i" to check if the URL starts with http or https. Among them,

• ^ represents the beginning of the matching string
• http represents matching the http string
• (s)? represents the optional s character
• :// represents two slash characters
• i represents case insensitivity

When the URL starts with http or https, "URL is valid!" will be output. .

Next, we will show how to check whether the URL contains the specified string. Suppose we want to verify whether the URL contains the "example" string:

$url = "https://www.example.com";
if(preg_match("/example/i", $url)) {
    echo "URL contains 'example'!";
} else {
    echo "URL does not contain 'example'!";
}

In this code, we use the regular expression "example/i" to check whether the URL contains the "example" string. When the URL contains the "example" string, "URL contains 'example'!" will be output.

But what should you do when you need to verify whether the URL contains multiple strings at the same time? In this case, we can use the "|" character to match any of the strings. For example, let's say we want to verify that a URL contains both the "example" and "com" strings:

$url = "https://www.example.com";
if(preg_match("/example|com/i", $url)) {
    echo "URL contains 'example' and 'com'!";
} else {
    echo "URL does not contain 'example' and 'com'!";
}

In this code, we use the regular expression "example|com/i" to check the URL Whether to contain both the "example" and "com" strings. When the URL contains both strings, "URL contains 'example' and 'com'!" will be output.

Overall, using regular expressions to verify whether a URL contains a specified string in PHP is a very useful skill. This article explains how to use regular expressions to verify whether a URL starts with http or https, verify whether a URL contains a specified string, and verify whether a URL contains multiple strings at the same time. Mastering these skills can help us better handle URLs in PHP development.

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