Core function for generating human-readable diff output.

Source: wp-includes/pluggable.php

wp_text_diff()

Displays a human-readable HTML representation of the difference between two strings.

Since: 2.6.0
Pluggable: Yes — can be overridden in a plugin

wp_text_diff( string $left_string, string $right_string, string|array $args = null ): string

Parameters

Args

Returns

• string — HTML table showing differences
• string (empty) — If strings are equivalent after whitespace normalization

Processing Flow

1. Parse arguments with wp_parse_args()
2. Load wp-diff.php if needed
3. Normalize whitespace on both strings
4. Split strings into lines
5. Create Text_Diff object
6. Render with WP_Text_Diff_Renderer_Table
7. Wrap output in accessible HTML table

Example: Basic Usage

$old_content = "Hello world.nThis is a test.";
$new_content = "Hello world.nThis is a modified test.";

$diff = wp_text_diff( $old_content, $new_content );
echo $diff;

Example: With Column Headers

$diff = wp_text_diff( $old_content, $new_content, array(
    'title'       => __( 'Content Changes' ),
    'title_left'  => __( 'Revision 42' ),
    'title_right' => __( 'Current Version' ),
) );

Example: Single Column View

// Useful for narrow layouts or mobile
$diff = wp_text_diff( $old_content, $new_content, array(
    'show_split_view' => false,
) );

Example: Check for Changes

$diff = wp_text_diff( $old_content, $new_content );

if ( empty( $diff ) ) {
    echo 'No changes detected.';
} else {
    echo $diff;
}

Overriding (Pluggable)

This function is pluggable and can be replaced entirely:

// In a must-use plugin (loaded before pluggable.php)
function wp_text_diff( $left_string, $right_string, $args = null ) {
    // Custom implementation
    // Perhaps using a different diff library
    return my_custom_diff( $left_string, $right_string, $args );
}

Internal Notes

• Whitespace is normalized before comparison via normalize_whitespace()
• The function loads wp-diff.php lazily only when needed
• Empty diff result (no changes) returns empty string, not empty table
• The is-split-view class is added to table when split view is enabled
• Column headers use <th> when content is provided, <td> when empty