Remove all except inside tag - php

Question

How to remove all from page except text inside <p> tag?
Page:
This is text.
<div class="text">This is text in 'div' tag</div>
<p>This is text in 'p' tag</p>
Expected result:
This is text in 'p' tag
Greetings.

Answer 1

Basically, you'll have to parse the markup. PHP comes with a good parser in the form of the DOMDocument class, so that's really quite easy:
$dom = new DOMDocument;
$dom->loadHTML($htmlString);
Next, get all p tags:
$paragraphs = $dom->getElementsByTagName('p');
This method returns a DOMNodeList object, which implements the Traversable interface, so you can use it as an array of DOMNode instances (DOMElement in this case):
$first = $paragraphs->item(0);//or $paragraphs[0] even
foreach ($paragraphs as $p) {
echo $p->textContent;//echo the inner text
}
If you only want the paragraph elements that do not contain child elements, then you can easily check that:
foreach ($paragraphs as $p) {
if (!$p->hasChildNodes()) {
echo $p->textContent; // or $p->nodeValue
}
}
A closely related answer with some more links/info: How to split an HTML string into chunks in PHP?

Answer 2

You can easily do this with the native php strip_tags function like so:
strip_tags("<p>This is text in 'p' tag</p>");
Which will return as you expected, "This is text in 'p' tag". NOTE: this is only useful when you have an outer-container div, and you use a little bit of dirty RegExp in order to strip not only the P, but the whole tags the user expected (ex. the div tag). This function has one argument, and a second optional argument. The first one is the string that you are stripping the tags from, and the second one specifies allowable tags that won't be stripped as a string. These tags will not be removed in the process. For more information on the strip_tags function click here. I hope you got the idea :)