Avoiding syntax errors with PHP and strings with quotation marks

Question

What is the best practice for manipulating strings with PHP (output mode) that might contain straight quote marks (single or double)? I'm not totally clear how EE stores and outputs these normally, and so I've run into PHP parse errors in certain situations.

Is the only reliable method to use {exp:xml_encode}? For example:

$excerpt = '{exp:xml_encode}{post_excerpt}{/exp:xml_encode}';

...and are those single quotes above around the EE code better than using double quotes?

EE's implementation of {exp:xml_encode} incorporates the PHP strip_tags() function, so this is not always ideal (e.g the excerpt above might have a phrase wrapped in <strong> tags. But at the same time, it seems there's no other way to store and manipulate the field content in PHP if it contains single or double quotes.

Answer 1

Try using the php function addslashes:

<?php
$str = "Is your name O'reilly?";

// Outputs: Is your name O\'reilly?
echo addslashes($str);
?>

So for EE you could have something like:

(UPDATE 1: the following does not work:)

<p>This is the title and excerpt of this entry: "
    <?php 
        $str = "<strong>". addslashes({title}) . "</strong> : ";
        $str .= addslashes({post_excerpt}); // combine title and post_excerpt
        echo  stripslashes($str); // remove the slashes.
    ?>
"</p>

UPDATE 1 the following does work:

Following the suggestion of th3mus1cman above, this does work in a plugin without needing addslashes:

On your template:
<p>This is the excerpt of this entry: "

    {exp:test_php}{post_excerpt}{/exp:test_php}

"</p>

In your test_php plugin: 
public function __construct()
{
    $ee_str = ee()->TMPL->tagdata;
    $new_str = "<strong>". $ee_str . "</strong>";

    $this->return_data = $new_str;
}