Highlight difference in string using php

function computeDiff($from, $to)
{
    $diffValues = array();
    $diffMask = array();

    $dm = array();
    $n1 = count($from);
    $n2 = count($to);

    for ($j = -1; $j < $n2; $j++) $dm[-1][$j] = 0;
    for ($i = -1; $i < $n1; $i++) $dm[$i][-1] = 0;
    for ($i = 0; $i < $n1; $i++)
    {
        for ($j = 0; $j < $n2; $j++)
        {
            if ($from[$i] == $to[$j])
            {
                $ad = $dm[$i - 1][$j - 1];
                $dm[$i][$j] = $ad + 1;
            }
            else
            {
                $a1 = $dm[$i - 1][$j];
                $a2 = $dm[$i][$j - 1];
                $dm[$i][$j] = max($a1, $a2);
            }
        }
    }

    $i = $n1 - 1;
    $j = $n2 - 1;
    while (($i > -1) || ($j > -1))
    {
        if ($j > -1)
        {
            if ($dm[$i][$j - 1] == $dm[$i][$j])
            {
                $diffValues[] = $to[$j];
                $diffMask[] = 1;
                $j--;  
                continue;              
            }
        }
        if ($i > -1)
        {
            if ($dm[$i - 1][$j] == $dm[$i][$j])
            {
                $diffValues[] = $from[$i];
                $diffMask[] = -1;
                $i--;
                continue;              
            }
        }
        {
            $diffValues[] = $from[$i];
            $diffMask[] = 0;
            $i--;
            $j--;
        }
    }    

    $diffValues = array_reverse($diffValues);
    $diffMask = array_reverse($diffMask);

    return array('values' => $diffValues, 'mask' => $diffMask);
}

function diffline($line1, $line2)
{
    $diff = computeDiff(str_split($line1), str_split($line2));
    $diffval = $diff['values'];
    $diffmask = $diff['mask'];

    $n = count($diffval);
    $pmc = 0;
    $result = '';
    for ($i = 0; $i < $n; $i++)
    {
        $mc = $diffmask[$i];
        if ($mc != $pmc)
        {
            switch ($pmc)
            {
                case -1: $result .= '</del>'; break;
                case 1: $result .= '</ins>'; break;
            }
            switch ($mc)
            {
                case -1: $result .= '<del>'; break;
                case 1: $result .= '<ins>'; break;
            }
        }
        $result .= $diffval[$i];

        $pmc = $mc;
    }
    switch ($pmc)
    {
        case -1: $result .= '</del>'; break;
        case 1: $result .= '</ins>'; break;
    }

    return $result;
}

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102

103

104

function computeDiff($from, $to)

{

$diffValues = array();

$diffMask = array();

$dm = array();

$n1 = count($from);

$n2 = count($to);

for ($j = -1; $j < $n2; $j++) $dm[-1][$j] = 0;

for ($i = -1; $i < $n1; $i++) $dm[$i][-1] = 0;

for ($i = 0; $i < $n1; $i++)

{

for ($j = 0; $j < $n2; $j++)

{

if ($from[$i] == $to[$j])

{

$ad = $dm[$i - 1][$j - 1];

$dm[$i][$j] = $ad + 1;

}

else

{

$a1 = $dm[$i - 1][$j];

$a2 = $dm[$i][$j - 1];

$dm[$i][$j] = max($a1, $a2);

}

$i = $n1 - 1;

$j = $n2 - 1;

while (($i > -1) || ($j > -1))

{

if ($j > -1)

{

if ($dm[$i][$j - 1] == $dm[$i][$j])

{

$diffValues[] = $to[$j];

$diffMask[] = 1;

$j--;

continue;

}

if ($i > -1)

{

if ($dm[$i - 1][$j] == $dm[$i][$j])

{

$diffValues[] = $from[$i];

$diffMask[] = -1;

$i--;

continue;

}

{

$diffValues[] = $from[$i];

$diffMask[] = 0;

$i--;

$j--;

}

$diffValues = array_reverse($diffValues);

$diffMask = array_reverse($diffMask);

return array('values' => $diffValues, 'mask' => $diffMask);

}

function diffline($line1, $line2)

{

$diff = computeDiff(str_split($line1), str_split($line2));

$diffval = $diff['values'];

$diffmask = $diff['mask'];

$n = count($diffval);

$pmc = 0;

$result = '';

for ($i = 0; $i < $n; $i++)

{

$mc = $diffmask[$i];

if ($mc != $pmc)

{

switch ($pmc)

{

case -1: $result .= '</del>'; break;

case 1: $result .= '</ins>'; break;

}

switch ($mc)

{

case -1: $result .= '<del>'; break;

case 1: $result .= '<ins>'; break;

}

$result .= $diffval[$i];

$pmc = $mc;

}

switch ($pmc)

{

case -1: $result .= '</del>'; break;

case 1: $result .= '</ins>'; break;

}

return $result;

}

Eg.:

<span class="pln">echo diffline</span><span class="pun">(</span><span class="str">'StackOverflow'</span><span class="pun">,</span> <span class="str">'ServerFault'</span><span class="pun">)</span>

1	<span class="pln">echo diffline</span><span class="pun">(</span><span class="str">'StackOverflow'</span><span class="pun">,</span> <span class="str">'ServerFault'</span><span class="pun">)</span>

Will output:

<span class="pln">S</span><span class="str">&lt;del&gt;</span><span class="pln">tackO</span><span class="pun">&lt;</span><span class="str">/del&gt;&lt;ins&gt;er&lt;/</span><span class="pln">ins</span><span class="pun">&gt;</span><span class="pln">ver</span><span class="str">&lt;del&gt;</span><span class="pln">f</span><span class="pun">&lt;</span><span class="str">/del&gt;&lt;ins&gt;Fau&lt;/</span><span class="pln">ins</span><span class="pun">&gt;</span><span class="pln">l</span><span class="str">&lt;del&gt;</span><span class="pln">ow</span><span class="pun">&lt;</span><span class="str">/del&gt;&lt;ins&gt;t&lt;/</span><span class="pln">ins</span><span class="pun">&gt;</span>

S<del>tackO</del><ins>er</ins>ver<del>f</del><ins>Fau</ins>l<del>ow</del><ins>t</ins>

References :

https://stackoverflow.com/questions/321294/highlight-the-difference-between-two-strings-in-php#

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