PHP html解析器代码

虽然笔者更主张使用高级语言做html的解析器；可今天笔者让我们web界的小强php也做一把html解析器，证明小强的功力是多么深厚^_^

算法思想的说明：

可以将整个算法理解为一个有限状态机，首先获取 “<”，然后解析小于号右边的字符串直到 “>” 为止。这样，便完成了一个html标签的解析过程。

具体过程各位请看下面的代码：

function dp($txt, $var)
{
$trans = get_html_translation_table(HTML_ENTITIES);
$encoded = strtr($var, $trans);
printf("<br>%s is now: %s", $txt, $encoded);
}

/*
author: http://www.cnphp.info
source: http://www.cnphp.info/php-html-parser-code-update.html
*/
function parse($html) {
$html2 = $html;
$tmp = $html2;

$c=0;

while (($tmp[$c] || $c < strlen($tmp))) {

if ($tmp[$c] == '<' || $istag) {
$istag = 0;

if ($tmp[$c++] == '!') {
// comment
if ($tmp[$c++] == '-' || $tmp[$c+1] == '-') {
$c+=2;
// trim($tmp) ??
while ($tmp[$c] == ' ') $c++;
$c--;

startCommentCallback();

// find the end of the comment
$t = $c;
while (($tmp[$t] || $t < strlen($tmp)) && !($tmp[$t] == '-' && $tmp[$t++] == '-' && $tmp[$t+2] == '>')) $t++;
if (($tmp[$t] || $t < strlen($tmp))) {
while ($tmp[$t] == ' ') $t--;
$comment = substr($tmp, $c, $t-$c);
while ($tmp[$t] == ' ') $t++;
$t+=2;
$c = $t;
}

commentCallback($comment);
endCommentCallback();

$c++;
} else {
$c--;
// handle starttag
}
} elseif ($tmp[$c] == '/' || $tmp[$c-1] == '/') {
if ($tmp[$c] == '/') $c++;
$t=$c;
while (($tmp[$t] || $t < strlen($tmp)) && $tmp[$t] != '>') $t++;

$tag = substr($tmp,$c,$t-$c);
endCallback($tag);
$t++;
$c = $t;
continue;
} else {
// starttag here
// maybe inseperate function because of above
if ($tmp[$c-1] != '<') $c--;

// comment function from above in seperate function call.
if ($tmp[$c] == '!' && $tmp[$c++] == '-') comment();

$t = $c;
$q = $c;    // $q belongs to $tag[$q]
$tagstart = $c;

$tag = substr($tmp,$c);

while ($tmp[$t] != '>' && $tmp[$t] != ' ') $t++;
if ($tmp[$t] == '>') {
$tag = substr($tmp, $c, $t-$c);
if ($tag[0] == '!') {
$tag = substr($tmp,$c+1, $t-($c+1));
$tagstart = $c+1;
declCallback($tag, "", 0);
} else startCallback($tag, "", 0);

// TEST was c = t
$c = $t+1;

continue;
} elseif ($tmp[$c] == ' ') {
while ($tmp[$c] == ' ') $c++;
} else {
if ($tmp[$q] == '!') {
$q++;
$tag = substr($tmp, $q, $q-$c);
declCallback ($tag, "", 0);
} else {
declCallback ($tag, "", 0);
}
break;
}

unset($args);
$numargs = 0;

while (($tmp[$c] || $c < strlen($tmp))) {
$istrue = 0;
$tagended = 0;
while ($tmp[$c] == ' ') $c++;
if (!$tmp[$c-1] == ' ') $c--;

// $arg = start of argument
$arg = $c;

// $q is used to find end of argument
if ($tmp[$arg] == '"' || $tmp[$arg] == '\'') {
$c++;
$arg = $c;
while (($tmp[$c] || $c < strlen($tmp)) && !($tmp[$c] == '"' && $tmp[$c-1] != '\\' && $tmp[$c] != '\'')) $c++;
// add arguments to table?

if ($tmp[$c] != '>') continue;
if ($tmp[$c+1] == '>') {
$c++;
}
break;
}

$val = "";
while ($tmp[$c] != '=' && $tmp[$c] != ' ' && $tmp[$c] != '>') $c++;
if ($tmp[$c] != ' ' && $tmp[$c] != '>') $istrue = 1;
if ($tmp[$c] == '>') $tagended = 1;

$q = $c;
$c++;

if ($istrue) {
if ($tmp[$c] != '\'' && $tmp[$c] != '"') {
while ($tmp[$c] != ' ' && $tmp[$c] != '>') $c++;
if ($tmp[$c] == '>') {
$val = substr($tmp,$q, $c-$q);
} else {
$c++;
$val = substr($tmp, $c, $c-$q);
continue;
}
} else {
$c++;
while ($tmp[$c] && ($tmp[$c] != '\'' || ($tmp[$c] == '\'' && $tmp[$c-1] == '\\')) && ($tmp[$c] != '"' || ($tmp[$c] == '"' && $tmp[$c-1] == '\\'))) $c++;
if ($tmp[$c] == '>') {
$val = substr($tmp,$q, $c-$q);
$c++;
// add args
break;

} elseif ($tmp[$c+1] == '>') {
$val = substr($tmp, $q, $c-$q);
$c++;
// add args
break;
} else {
$val = substr($tmp, $q, $c-$q);
$c+=2;
// add args
}
}
} else {
// add args
if (!$tagended) continue;
$tagended = 0;
$c--;
break;
}
}

// is q allowed here?
$q=0;
if ($tag[$q] == '!') {
$q++;
// FIXME
$tag = substr($tag, $q);
// FIX THIS TOO
declCallback($tag, "", 0);
} else {
// and this
startCallback($tag, "", 0);
}

// clear arg list;
$c++;
continue;
}
} else {
// check for newline char
if ($tmp[$c] == '\n') {
$c++;
continue;
}

$text = $tmp;
$q = $c;

if ($text[$q] == '!') {
$q--;
if ($text[$q-1] == '<') {
$q--;
continue;
}
} 

while ($tmp[$c] == ' ' && $tmp[$c] != '<' && ($tmp[$c] || $c < strlen($tmp))) $c++;
if ($tmp[$c] == '<' && $tmp[$c+1]) {
continue;
} else if (!($tmp[$c] || $c < strlen($tmp))) break;

// text start
textStartCallback();

for (;;) {
while (($tmp[$c] || $c < strlen($tmp)) && $tmp[$c] != '<') $c++;
if ($tmp[$c] == '<') {
if ($tmp[$c+1] == ' ') {
$c++;
continue;
} else $istag = 1;
}
break;
}

$text = substr($tmp, $q, $c-$q);

// text callback
textCallback($text);

// text end
textEndCallback();
$c++;
continue;

}

}

return;
}

当然，如果你觉得这个html解析器太简单了请看笔者写的《PHP Simple HTML DOM解析器使用入门》