PHP Text Diff Highlight class can find and view the difference between text strings. It takes two text strings and uses the diff algorithm to find the differences between them and return a list of changes to patch the original string to become the final string. The patch list shows what text should be added or removed to change one string into the other. The difference between the text strings may be computed in three modes: by character, by word, or by line. The class may also format the strings to view them as HTML, showing which characters are added and removed with special insertion and deletion styles. The example page works as a tool to interactively view the changes as the user changes the texts before and after the changes are applied.
