Simple PHP string parsing - php

Question

I'm trying to parse the following format with PHP:
// This is a comment
{
this is an entry
}
{
this is another entry
}
{
entry
{entry within entry}
{entry within entry}
}
Maybe is just the lack of caffeine, but i can't think of a decent way of getting the contents of the curly braces.

Answer 1

This is quite a common parsing task, basically you need to keep track of the various states you can be in and use a combination of constants and function calls to maintain them.
Here is some rather inelegant code that does just that:
<?php
$input = file_get_contents('input.txt');
define('STATE_CDATA', 0);
define('STATE_COMMENT', 1);
function parseBrace($input, &$i)
{
$parsed = array(
'cdata' => '',
'children' => array()
);
$length = strlen($input);
$state = STATE_CDATA;
for(++$i; $i < $length; ++$i) {
switch($input[$i]) {
case '/':
if ('/' === $input[$i+1]) {
$state = STATE_COMMENT;
++$i;
} if (STATE_CDATA === $state) {
$parsed['cdata'] .= $input[$i];
}
break;
case '{':
if (STATE_CDATA === $state) {
$parsed['children'][] = parseBrace($input, $i);
}
break;
case '}':
if (STATE_CDATA === $state) {
break 2; // for
}
break;
case "\n":
if (STATE_CDATA === $state) {
$parsed['cdata'] .= $input[$i];
}
$state = STATE_CDATA;
break;
default:
if (STATE_CDATA === $state) {
$parsed['cdata'] .= $input[$i];
}
}
}
return $parsed;
}
function parseInput($input)
{
$parsed = array(
'cdata' => '',
'children' => array()
);
$state = STATE_CDATA;
$length = strlen($input);
for($i = 0; $i < $length; ++$i) {
switch($input[$i]) {
case '/':
if ('/' === $input[$i+1]) {
$state = STATE_COMMENT;
++$i;
} if (STATE_CDATA === $state) {
$parsed['cdata'] .= $input[$i];
}
break;
case '{':
if (STATE_CDATA === $state) {
$parsed['children'][] = parseBrace($input, $i);
}
break;
case "\n":
if (STATE_CDATA === $state) {
$parsed['cdata'] .= $input[$i];
}
$state = STATE_CDATA;
break;
default:
if (STATE_CDATA === $state) {
$parsed['cdata'] .= $input[$i];
}
}
}
return $parsed;
}
print_r(parseInput($input));
This produces the following output:
Array
(
[cdata] =>
[children] => Array
(
[0] => Array
(
[cdata] =>
this is an entry
[children] => Array
(
)
)
[1] => Array
(
[cdata] =>
this is another entry
[children] => Array
(
)
)
[2] => Array
(
[cdata] =>
entry
[children] => Array
(
[0] => Array
(
[cdata] => entry within entry
[children] => Array
(
)
)
[1] => Array
(
[cdata] => entry within entry
[children] => Array
(
)
)
)
)
)
)
You'll probably want to clean up all the whitespace but some well placed trim's will sort that for you.

Answer 2

This may not be the best solution for large amount of content, but it works.
<?php
$text = "I am out of the brackets {hi i am in the brackets} Back out { Back in}";
print $text . '<hr />';
$tmp = explode("{",$text);
$tmp2 = array();
$wantedText = array();
for($i = 0; $i < count($tmp); $i++){
if(stristr($tmp[$i],"}")){
$tmp2 = explode("}",$tmp[$i]);
array_push($wantedText,$tmp2[0]);
}
}
print_r($wantedText);
?>
Results:
Array ( [0] => hi i am in the brackets [1] => Back in )