Table-based renderer for displaying diff output in a two-column HTML table format.

Source: wp-includes/class-wp-text-diff-renderer-table.php
Since: 2.6.0
Extends: Text_Diff_Renderer

Properties

Public Properties

Protected Properties

Methods

__construct()

Creates a new table renderer with optional configuration.

public function __construct( array $params = array() )

Params:

render()

Renders the diff as HTML table rows. Inherited from Text_Diff_Renderer.

public function render( Text_Diff $diff ): string

Returns: HTML string of table rows (<tr> elements).

addedLine()

Generates HTML for an added line cell.

public function addedLine( string $line ): string

Returns: <td class='diff-addedline'>...</td> with plus icon and screen reader text.

deletedLine()

Generates HTML for a deleted line cell.

public function deletedLine( string $line ): string

Returns: <td class='diff-deletedline'>...</td> with minus icon and screen reader text.

contextLine()

Generates HTML for an unchanged context line cell.

public function contextLine( string $line ): string

Returns: <td class='diff-context'>...</td> with screen reader text.

emptyLine()

Generates HTML for an empty placeholder cell.

public function emptyLine(): string

Returns: <td>&nbsp;</td>

_added()

Renders added lines with optional encoding.

public function _added( array $lines, bool $encode = true ): string

Returns: HTML rows for added content.

Applies Filter: process_text_diff_html with context 'added'

_deleted()

Renders deleted lines with optional encoding.

public function _deleted( array $lines, bool $encode = true ): string

Returns: HTML rows for deleted content.

Applies Filter: process_text_diff_html with context 'deleted'

_context()

Renders unchanged context lines with optional encoding.

public function _context( array $lines, bool $encode = true ): string

Returns: HTML rows for context (duplicated in both columns for split view).

Applies Filter: process_text_diff_html with context 'unchanged'

_changed()

Processes changed lines with word-level diff highlighting.

public function _changed( array $orig, array $final ): string

Returns: HTML rows with <ins> and <del> tags for word-level changes.

Algorithm:

1. Interleave lines to match similar content
2. Compute word-level diffs using inline renderer
3. Apply threshold check (skip highlighting if too different)
4. Render side-by-side or stacked based on view mode

interleave_changed_lines()

Matches original and final lines to align similar content.

public function interleave_changed_lines( array $orig, array $final ): array

Returns: Array with four elements:

compute_string_distance()

Computes a distance metric between two strings.

public function compute_string_distance( string $string1, string $string2 ): int

Returns: Distance score (lower = more similar). Based on L1-norm of character frequency difference.

Uses caching for performance with $count_cache and $difference_cache.

difference()

Computes absolute difference between two values.

public function difference( int $a, int $b ): int

Used internally by compute_string_distance().

Magic Methods

For backward compatibility, protected properties are accessible via magic methods:

Deprecated since 6.4.0 — Accessing undefined dynamic properties triggers deprecation notice.

Diff Threshold

The $_diff_threshold (default 0.6) controls when word-level highlighting is shown:

// If more than 60% of content changed, skip word highlighting
if ( $diff_ratio > $this->_diff_threshold ) {
    continue; // Show as plain deleted/added without <ins>/<del>
}

This prevents confusing output when lines are completely rewritten.

Split vs. Single View

Split view (default):

<tr>
    <td class="diff-deletedline">old content</td>
    <td class="diff-addedline">new content</td>
</tr>

Single column view:

<tr>
    <td class="diff-deletedline">old content</td>
</tr>
<tr>
    <td class="diff-addedline">new content</td>
</tr>

Extending

class My_Diff_Renderer extends WP_Text_Diff_Renderer_Table {
    
    // Lower threshold for more word-level diffs
    protected $_diff_threshold = 0.8;
    
    // Custom added line styling
    public function addedLine( $line ) {
        return "<td class='my-added'>{$line}</td>";
    }
}

// Use custom renderer
$renderer = new My_Diff_Renderer();
$output = $renderer->render( $text_diff );