Once I needed a decent text diffing solution for SafePatch and after some searching couldn’t find one. So I’ve decided to write my own. It might not be very accurate but it’s very easy to use and has two modes – finding changes by line or inline (within one line). It also comes with built-in HTML generation although you need to style it yourself with CSS.

It has no dependencies and works out of the box in PHP 5.2 and up – simply include it and you’re ready to go.

Download QuickDiff here. Released in public domain. You can also check/fork/report issues to GitHub.

Class methods

Inline	Diffes two flat strings treating line breaks as regular characters. Returns an array; each member is an array which 1^st element specifies the type of difference found (`-` for removed piece, `+` for added, `=` for equal and `change` when a string portion was altered) and 2^nd element holds what was deleted/added/equal. For `change` also a 3^rd element is present indicating the new value of that string portion.
InlineHTML	Calls `Inline()` to calculate the difference and then transforms its result into a HTML string with `xml<span>` tags around each changed portion with `class` indicating the type of change (`del`, `add`, `equ` or `change`).
Full	Diffes two texts by-line. Returns an array; each member has similar form to that of `Inline()`.
FullHTML	Calculates difference between two texts by calling `Full()` and returns a HTML string. Collapses lengthy runs of equal lines and calculates in-line differences with `Inline()`. Its $options array can have these members: classes – maps piece types (like `-` and `+`) onto tag class names (like `del` and `add`; note that it only affects by-line differ, not `InlineHTML()` which uess hardcoded mappings lineNumbers – a boolean indicating if line numbers should be output or not collapseLines – a number specifying how long a sequence of unchanged lines can be; longer sequences get a dashed-out separator in place of omitted lines
FullHtmlWrapped	Similar to `FullHTML()` but wraps the entire listing into a `xml<pre>` tag, also checking whether or not an input is binary and outputting a message without diffing it if it’s the case. Its $options array can have these members plus all those of `FullHTML()`: tag – tag name to wrap the listing into tagClasses – classes to set to it, e.g. `xml<pre class="qdiff">`; can be empty binMsg – message string to output if the input is binary; it’s output as a `xml<p>` tag having tagClasses plus added «bin» class

Inline

Diffes two flat strings treating line breaks as regular characters. Returns an array; each member is an array which 1^st element specifies the type of difference found (- for removed piece, + for added, = for equal and change when a string portion was altered) and 2^nd element holds what was deleted/added/equal. For change also a 3^rd element is present indicating the new value of that string portion.

InlineHTML

Calls Inline() to calculate the difference and then transforms its result into a HTML string with xml<span> tags around each changed portion with class indicating the type of change (del, add, equ or change).

Full

Diffes two texts by-line. Returns an array; each member has similar form to that of Inline().

FullHTML

Calculates difference between two texts by calling Full() and returns a HTML string. Collapses lengthy runs of equal lines and calculates in-line differences with Inline(). Its $options array can have these members:

classes – maps piece types (like - and +) onto tag class names (like del and add; note that it only affects by-line differ, not InlineHTML() which uess hardcoded mappings
lineNumbers – a boolean indicating if line numbers should be output or not
collapseLines – a number specifying how long a sequence of unchanged lines can be; longer sequences get a dashed-out separator in place of omitted lines

FullHtmlWrapped

Similar to FullHTML() but wraps the entire listing into a xml<pre> tag, also checking whether or not an input is binary and outputting a message without diffing it if it’s the case. Its $options array can have these members plus all those of FullHTML():

tag – tag name to wrap the listing into
tagClasses – classes to set to it, e.g. xml<pre class="qdiff">; can be empty
binMsg – message string to output if the input is binary; it’s output as a xml<p> tag having tagClasses plus added «bin» class

HTML-outputting functions convert certain symbols defined in PHPQuickDiff::$htmlReplaces to more representable text equivalents. Particularly, spaces become middle dots (·), line breaks – xml<br /> and tabs become two spaces (no ·).

Usage examples

PHP

require_once 'quickdiff.php';

echo QuickDiff::FullHtmlWrapped("line1\nline2", "line1\nKABOOM\nline2");
  //=> <pre class="qdiff">...</pre>
echo QuickDiff::FullHtmlWrapped("\bin\xA\ry\0u\tput", "line1\nKABOOM\nline2");
  //=> <p class="qdiff bin">Diff is unavailable for binary data.</p>
echo QuickDiff::InlineHTML("this plus that", "plus that and this");
  //=> <span class="add">this<i>&middot;</i></span>...