Using ob_start() and ob_get_clean() in PHP

✅ 1. Flexible Output Control

You can capture HTML output and decide:

• When to send it to the browser
• Whether to modify it
• Or simply return it as a string

Example:
WordPress shortcodes and custom blocks require a return value, not direct echo.

add_shortcode('greeting', function() {
    ob_start();
    echo "<div>Hello, User!</div>";
    return ob_get_clean(); // safe return of HTML
});

✅ 2. Clean Separation of Logic and Presentation

You can write HTML directly inside PHP without echoing line by line.

Without buffering:

$html = "<div>";
$html .= "<h1>Hello</h1>";
$html .= "</div>";
return $html;

With buffering:

ob_start();
?>
<div>
  <h1>Hello</h1>
</div>
<?php
return ob_get_clean();

It’s more readable and natural for writing HTML.

✅ 3. Reusable & Testable Code

Buffering allows you to build HTML fragments that can be reused, modified, or tested before output.

$html = get_custom_html_section(); // a function that returns buffered HTML
if ($is_admin) {
    $html = str_replace('User', 'Admin', $html);
}
echo $html;

✅ 4. Prevent Accidental Output

Sometimes libraries or plugins echo unwanted content. Output buffering can “trap” that output before it ruins headers or breaks JSON.

ob_start();
some_third_party_function(); // echoes something
$output = ob_get_clean(); // capture & control it

You can then safely log, ignore, or parse it.

✅ 5. Useful in Unit Testing or AJAX

Capture HTML returned by functions and compare it in tests:

ob_start();
render_product_card($product);
$html = ob_get_clean();
$this->assertStringContainsString('Product Title', $html);

Also useful when responding to AJAX with generated HTML.

✅ 6. Better for Template Partials

You can wrap a template in output buffering and return it cleanly:

function render_custom_template($data) {
    ob_start();
    include locate_template('partials/my-section.php');
    return ob_get_clean();
}

🛠 Summary: Benefits at a Glance