php match src replacement

In website development, we often encounter situations where we need to replace certain parts of the page code in batches. For example, we need to replace all image addresses (src) in the page with new addresses. At this time, we can use the powerful regular expressions provided by PHP to achieve this.

First, we need to obtain the HTML code that needs to be modified. You can use the file_get_contents() function to read from a file or get HTML code from a URL.

$html = file_get_contents('http://www.example.com/page.html');

Then, we need to construct a regular expression to match all image addresses on the page. In HTML pages, the src attributes of all image tags appear in the form of src="xxxxxx". Therefore, we can construct a regular expression to match all src attributes, as follows:

$pattern = '/src=[\'"]([^\'"]+)[\'"]/i';

In this regular expression, square brackets [] are used to represent a character set, which includes single quotes, double quotes Quotation marks and other characters except single and double quotes. The plus sign is used to match the previous set of characters at least once. Use parentheses () to indicate grouping and extract the value of the src attribute. The /i flag is used to indicate case insensitivity.

Next, we need to use the preg_replace_callback() function to implement the replacement operation. This function can call a callback function to perform the replacement operation for each matched result. In this callback function, we can get the value of the matching src attribute and perform the replacement operation.

$newHtml = preg_replace_callback($pattern, function($matches) {
    $oldSrc = $matches[1];
    $newSrc = getNewSrc($oldSrc);
    return 'src="' . $newSrc . '"';
}, $html);

In this callback function, we first obtain the value of the matched src attribute $oldSrc, and then call a getNewSrc() function to obtain the new image address $newSrc and assign it to the src attribute. , and returns the replaced string.

After completing the replacement operation, we can output or save the new HTML code to a file.

echo $newHtml;
file_put_contents('new.html', $newHtml);

The complete code is as follows:

$html = file_get_contents('http://www.example.com/page.html');

$pattern = '/src=[\'"]([^\'"]+)[\'"]/i';

$newHtml = preg_replace_callback($pattern, function($matches) {
    $oldSrc = $matches[1];
    $newSrc = getNewSrc($oldSrc);
    return 'src="' . $newSrc . '"';
}, $html);

echo $newHtml;
file_put_contents('new.html', $newHtml);

function getNewSrc($oldSrc) {
    // do something to get the new src
    return $newSrc;
}

By using PHP’s regular expressions, we can easily replace certain parts of the page in batches, making the development and maintenance of the website more efficient. .

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