PHP array key is NULL, array appears empty - php

Question

I'm rather new to PHP and I am kind of stuck here writing this simple script; what I am trying to ultimately do is go through the content of a string and find the positions of all the occurrences I have listed in my $definitions array then map those positions in a separate array and return it...
rather simple but I am not sure where the problem arises, when i print_r on the array in different parts of code, thinking its a scope issue, I keep seeing that the key value of the array is NULL and also when I try and access a value of the array I am sure exists for a given key, i also get nothing; any help would be appreciated...
thank you!
<?php
class html2DokuWiki {
function definition_map($content){
$definitions = array("<title" => " ","<h" => array("=", 6),"<p" => "\n\n","<b" => "**","<strong" => "**","<em" => "//","<u" => "__","<img" => " ","<a" => " ","<ul" => " ","<ol" => "*","<li" => "-","<dl" => " ","<dt" => " ","<dd" => " ");
$element_pos = array();
foreach($definitions as $html_element){
$offset = 0;
$counter = 0;
$element_pos[(string)$html_element] = array(); //ask phil why do i need to cast in order to use the object?
while($offset = strpos($content, $html_element, $offset + 1)){
$element_pos[(string)$html_element][] = $offset;
};
};
//print_r($element_pos);
echo $element_pos["<p"][0];
return $element_pos;}
function run($page){
return $this->definition_map($page);}
};
$debug = new html2DokuWiki();
$url = "http://www.unixwiz.net/techtips/sql-injection.html";
$content = file_get_contents($url);
//echo $content;
//print_r($debug->run($content));
$test = $debug->run($content);
echo "<p> THIS:".$test["<p"][0]."</p>";
//print_r($test);
?>

Answer 1

If it's the key you want to use as $html_element as an index you should do:
foreach($definitions as $html_element => $value){