How to Replace and Modify Content Between Two Delimiters in PHP

A while ago I have written a short tutorial of how you can write a short PHP function to extract content from specific delimiters. I has come to my attention that many people are looking for a way to replace and even modify content between 2 delimiters. Therefore I have decided to write a script that can help them with this endeavor. Uses regular expressions to find and parse the matched content.

Replace all the content found between the delimiters

function replace_content_inside_delimiters($start, $end, $new, $source) {
return preg_replace('#('.preg_quote($start).')(.*?)('.preg_quote($end).')#si', '$1'.$new.'$3', $source);
}

As you can see the function uses 4 arguments. The first 2 two are the delimiters (the beginning and the ending one), the 3d is the replacement string and the last one is the main source that is parsed.

$data = '<body><div class="wrap"><div class="inside">Lorem ipsum dolor sit amet, consectetur adipiscing elit.</div></div></body>';

$start = '<div class="inside">';
$end =  '</div>';

$replace_with = 'PHP: Hypertext Preprocessor';

$str = replace_content_inside_delimiters($start, $end, 'PHP: Hypertext Preprocessor', $data);

echo $str;

// Result: <body><div class="wrap"><div class="inside">PHP: Hypertext Preprocessor</div></div></body>'

Filter the content found between the delimiters

In case you need to modify the text between the delimiters here’s how you can do it:

$source = '<div class="subtitle">PHP is a widely-used general-purpose scripting language for web development.</div>';

$start = '<div class="subtitle">';
$end = '</div>';

$data = preg_replace('#('.preg_quote($start).')(.*?)('.preg_quote($end).')#si', '$1'.parse_content($new).'$3', $source);

function parse_content($content) {
$words = array('PHP', 'scripting', 'development'); // Let's bold some words!

foreach($words as $word) {
$content = str_replace($word, '<strong>'.$word.'</strong>', $content);
}

return $content;
}

How it works?

The regex uses the \s and the \i modifiers. The former (aka: DOTALL) makes dot a special character that matches newlines too. The later matches the characters in insensitive mode.