Replace markdown with html in wordpress - php

Question

I am trying to replace all the wiki markdown text from my custom post. Example:
== My Subheading ==
=== My sub Subheading ===
==== another heading ====
I am trying to change that content like below:
My Subheading My sub Subheading another
heading
So, I tried to use below function. But, didn't worked!
I am seeing:
Parse error: syntax error, unexpected token "{", expecting "("
I am not much familiar with WP custom function. Can u guys please help me?
function the_content{
private $patterns, $replacements;
public function __construct($analyze=false) {
$this->patterns=array(
"/\r\n/",
// Headings
"/^==== (.+?) ====$/m",
"/^=== (.+?) ===$/m",
"/^== (.+?) ==$/m",
// Formatting
"/\'\'\'\'\'(.+?)\'\'\'\'\'/s",
"/\'\'\'(.+?)\'\'\'/s",
"/\'\'(.+?)\'\'/s",
// Special
"/^----+(\s*)$/m",
"/\[\[(file|img):((ht|f)tp(s?):\/\/(.+?))( (.+))*\]\]/i",
"/\[((news|(ht|f)tp(s?)|irc):\/\/(.+?))( (.+))\]/i",
"/\[((news|(ht|f)tp(s?)|irc):\/\/(.+?))\]/i",
// Indentations
"/[\n\r]: *.+([\n\r]:+.+)*/",
"/^:(?!:) *(.+)$/m",
"/([\n\r]:: *.+)+/",
"/^:: *(.+)$/m",
// Ordered list
"/[\n\r]?#.+([\n|\r]#.+)+/",
"/[\n\r]#(?!#) *(.+)(([\n\r]#{2,}.+)+)/",
// Unordered list
"/[\n\r]?\*.+([\n|\r]\*.+)+/",
"/[\n\r]\*(?!\*) *(.+)(([\n\r]\*{2,}.+)+)/",
// List items
"/^[#\*]+ *(.+)$/m",
"/^(?!<li|dd).+(?=(<a|strong|em|img)).+$/mi",
"/^[^><\n\r]+$/m",
);
$this->replacements=array(
"\n",
// Headings
"<h3>$1</h3>",
"<h2>$1</h2>",
"<h1>$1</h1>",
//Formatting
"<strong><em>$1</em></strong>",
"<strong>$1</strong>",
"<em>$1</em>",
// Special
"<hr/>",
"<img src=\"$2\" alt=\"$6\"/>",
"$7",
"$1",
// Indentations
"\n<dl>$0\n</dl>",
"<dd>$1</dd>",
"\n<dd><dl>$0\n</dl></dd>",
"<dd>$1</dd>",
// Ordered list
"\n<ol>\n$0\n</ol>",
"\n<li>$1\n<ol>$2\n</ol>\n</li>",
// Unordered list
"\n<ul>\n$0\n</ul>",
"\n<li>$1\n<ul>$2\n</ul>\n</li>",
// List items
"<li>$1</li>",
// Newlines
"$0<br/>",
"$0<br/>",
);
if($analyze) {
foreach($this->patterns as $k=>$v) {
$this->patterns[$k].="S";
}
}
}
public function parse($input) {
if(!empty($input))
$output=preg_replace($this->patterns,$this->replacements,$input);
else
$output=false;
return $output;
}
}
Mainly I am trying to use a filter on the_content, which will convert markdown text to simple HTML using regex replace.

Answer 1

There were a few issues.
You weren't declaring your class properly (it is not a "function").
There was trailing space after == My Subheading == (before the end of line marker -- you need to allow zero or more spaces before $)
Please educate yourself on PHP's PSR-12 coding standards -- this will help you to write clean, consistent, and professional code.
Code: (Demo)
$text = <<<TEXT
== My Subheading ==
=== My sub Subheading ===
==== another heading ====
TEXT;
class ContentParser
{
private $patterns = [];
private $replacements = [];
public function __construct() {
$this->patterns = [
// Headings
"/^==== (.+?) ====\h*$/m",
"/^=== (.+?) ===\h*$/m",
"/^== (.+?) ==\h*$/m",
];
$this->replacements = [
// Headings
"<h3>$1</h3>",
"<h2>$1</h2>",
"<h1>$1</h1>",
];
}
public function parse($input) {
if (!empty($input)) {
$output = preg_replace($this->patterns, $this->replacements, $input);
} else {
$output = false; // I don't recommend returning a boolean when otherwise returning strings
}
return $output;
}
}
$object = new ContentParser();
var_export($object->parse($text));
Output: (the single quotes are from var_export(), you can use echo instead)
'<h1>My Subheading</h1>
<h2>My sub Subheading</h2>
<h3>another heading</h3>'